طلاق والدین، اندازه خاندان، منابع خانواده و عملکرد تحصیلی کودکان

Abstract Using data from 19,839 adolescents from the National Education Longitudinal Study, this study investigates whether the effects of parental divorce on adolescents’ academic test performance vary by sibship size. Analyses show that the negative effect of divorce on adolescent performance attenuates as sibship size increases. On the other side of the interaction, the inverse relationship between sibship size and test performance is weaker in disrupted than in two-biological-parent families. Trends of such interactions are evident when sibship size is examined either as a continuous or a categorical measure. Finally, the observed interactions on adolescents’ academic performance are completely explained by variations in parental financial, human, cultural, and social resources. In sum, this study underlines the importance of treating the effect of parental divorce as a variable and calls for more research to identify child and family features that may change the magnitude of such an effect.

1. Introduction A substantial amount of research has investigated whether parental divorce or separation affects children’s chances for educational success (e.g., Cherlin et al., 1991, Kurdek et al., 1995, McLanahan and Sandefur, 1994, Raley et al., 2005, Sun and Li, 2001 and Teachman et al., 1996). A growing section of this research has now moved beyond an earlier model that depicts the consequences of parental divorce as uniform and undifferentiated for all children (Furstenberg and Kiernan, 2001). Instead, many scholars now argue that the effect of divorce on children’s educational progress may vary contingent upon children’s gender (e.g., Morrison and Cherlin, 1995 and Zaslow, 1988), age (e.g., Allison and Furstenberg, 1989), race and ethnicity (e.g., Sun and Li, 2007), and the number of postdivorce family transitions (Kurdek et al., 1995 and Sun and Li, 2008). Another important family feature that may potentially alter the effect of divorce, but has not yet been rigorously examined, is the number of siblings a child has (hereafter referred to as sibship size). Specifically, we expect the negative effect of divorce on children’s educational outcomes to attenuate as sibship size increases, for two reasons. First, siblings may provide emotional support and comfort to one another during family crises such as parental divorce. The fact that siblings within the same family are going through this difficult process with a child may reduce the stress of divorce on the child and therefore, ease its negative effect (Kempton et al., 1991). Second, large sibship size generally dilutes valuable parental resources available for each child in a family (e.g., Blake, 1989 and Downey, 1995a) and the actual amount of parental resources divided by a given sibship size varies by the overall levels of such resources in different families. For instance, the levels of financial, human, and social resources are generally lower in disrupted than in two-biological-parent families (e.g., Coleman, 1988 and McLanahan and Sandefur, 1994). Thus, a large sibship size (e.g., five siblings) in both disrupted and two-biological-parent families will dilute the same proportion of resources, but the magnitude of dilution in disrupted families will be smaller, because they have fewer resources from the outset. Based on this argument, the extent of resource disadvantages in divorced relative to two-biological-parent families should be less severe in large than in small families. Given that resource deprivation in divorced families has been identified as a key reason for academic disadvantages in such families (e.g., Astone and McLanahan, 1991 and McLanahan and Sandefur, 1994), the divorce effect on children’s education should be smaller for children with many siblings than for their peers with just one or two siblings. Although prior divorce and sibship-size studies have separately investigated how resource deprivation in disrupted families and resource dilution in large households negatively affect children’s educational progress (e.g., Blake, 1981, Blake, 1989, Downey, 1995a, McLanahan and Sandefur, 1994, Park, 2008, Sun and Li, 2001, Steelman and Powell, 1989 and Xu, 2008), few of these studies have integrated the interrelated effects of parental divorce, sibship size, and parental resources in their investigations. Consequently, little is known to date about whether the effect of parental divorce on children’s academic progress varies by sibship size and whether such potential interactions are further related to family resources. Using data from 19,839 adolescents from the National Education Longitudinal Study (NELS), we examine the potential interaction effects between parental divorce and sibship size on adolescents’ test performance. Specifically, we investigate: (1) whether the effect of divorce lessens in magnitude as sibship size increases; and (2) whether various levels of parental financial, human, cultural, and social resources mediate the interaction effects of divorce and sibship size.

5. Results 5.1. Descriptive analyses Before turning to the two research questions, we first report the means and standard deviations of two test performance measures and the number of cases in each of the 14 subcategories of divorce status and sibship size (see Table 2). Simple t-tests are also conducted to estimate mean performance differences between children in two-biological-parent and disrupted families by each sibship size cell. To present the trends of sibship-size slopes, these means of test scores are also plotted in Fig. 1. Table 2. Descriptive statistics of adolescents’ reading and math performance by parental divorce status and by sibship size.a Family type Reading Math Number of siblings Number of siblings 0 1 2 3 4 5 6 or + 0 1 2 3 4 5 6 or + Two-biological-parent families Mean 28.53 28.63 27.41 26.37 25.47 24.45 23.98 37.39 38.16 37.07 35.72 34.53 32.79 31.94 Std 8.49 8.55 8.42 8.35 8.40 7.84 8.35 11.53 11.93 11.95 11.66 11.61 10.56 11.03 n 803 5032 3979 1994 894 480 718 802 5034 3981 1992 891 478 719 Disrupted families Mean 27.25 26.08 25.69 24.91 24.45 23.96 23.65 34.85 34.28 33.46 32.47 32.43 32.14 31.29 Std 8.68 8.44 8.51 8.61 8.14 7.99 8.08 11.35 11.49 11.43 10.81 10.82 10.52 11.09 N 428 1455 1428 999 633 376 587 427 1456 1429 997 637 374 586 Mean differences by divorce status −1.28⁎ −255⁎⁎⁎ −1.72⁎⁎⁎ −1.46⁎⁎⁎ −1.02⁎ −0.48 −0.32 −2.54⁎⁎⁎ −3.88⁎⁎⁎ −3.61⁎⁎⁎ −3.25⁎⁎⁎ −2.10⁎⁎⁎ −0.65 −0.65 ∗∗ p < 0.01. a All means were weighted by base-year sampling weights. ⁎ p < 0.05. ⁎⁎⁎ p < 0.001. Table options Means of reading and math test scores by divorce status and sibship size. Fig. 1. Means of reading and math test scores by divorce status and sibship size. Figure options As shown in Fig. 1, the means of reading and math performances in disrupted families decline almost linearly as sibship size increases. Similarly, the inverse relationships between sibship size and the two test performances in two-biological-parent families are also approximately linear, although these patterns are somewhat disrupted by the performance levels of only children. Consistent with several prior studies (e.g., Blake, 1989), only children in two-biological-parent families perform somewhat less well than peers in two-child households. Despite this, the overall sibship-size slopes on both reading and math performances are generally flatter in disrupted than in two-biological-parent households. Consequently, the mean performance differences between two-biological-parent and disrupted families (i.e., the divorce effect) are generally greater in magnitude in small than in large families. In fact, this difference in both reading and math is very small in magnitude and no longer statistically significant when adolescents have five or more siblings (see the bottom row of Table 2). Although these general trends are consistent with our earlier expectation for an interaction effect, the reader is reminded that these findings are not adjusted for family financial and social resources. In order to examine these trends rigorously, we turn to multivariate models. 5.2. Differences in divorce effect by continuous measure of sibship size We start the multivariate analyses with our first research question: Does the effect of parental divorce on children’s academic performance vary by sibship size, net of background features of students and their schools? Before we answer this question, we replicate prior studies by examining the main effects of parental disruption and sibship size on adolescent performance. Such an analysis provides baselines of these two main effects that help the reader interpret the interaction effects in subsequent models. Because our descriptive analyses show an approximately linear relationship between sibship size and adolescent performance, we first include sibship size as a continuous variable in this analysis. Specifically, we use OLS models2 and respectively regress students’ reading and math performances on parents’ disruption status, sibship size, and the six controls. Table 3 summarizes the findings in Model 1. Table 3. Unstandardized regression coefficients of regressions of adolescents’ academic performance on parental divorce status, sibship size (continuous), and interactions. Independent variables Reading Math Model 1a Model 2a Model 1a Model 2a Intercept 28.99⁎⁎⁎ 29.27⁎⁎⁎ 40.41⁎⁎⁎ 40.74⁎⁎⁎ Parental divorce status −1.03⁎⁎⁎ −1.66⁎⁎⁎ −2.09⁎⁎⁎ −3.07⁎⁎⁎ Sibship size (continuous) −0.52⁎⁎⁎ −0.62⁎⁎⁎ −0.54⁎⁎⁎ −0.70⁎⁎⁎ Female status 1.74⁎⁎⁎ 1.74⁎⁎⁎ −0.56⁎⁎⁎ −0.57⁎⁎⁎ Asian American 0.44 0.44 3.04⁎⁎⁎ 3.04⁎⁎⁎ African American −4.96⁎⁎⁎ −4.96⁎⁎⁎ −7.89⁎⁎⁎ −7.88⁎⁎⁎ Hispanic American −3.47⁎⁎⁎ −3.45⁎⁎⁎ −5.69⁎⁎⁎ −5.65⁎⁎⁎ Native American −4.87⁎⁎⁎ −4.85⁎⁎⁎ −6.84⁎⁎⁎ −6.81⁎⁎⁎ Adolescent has disability −4.32⁎⁎⁎ −4.33⁎⁎⁎ −6.28⁎⁎⁎ −6.29⁎⁎⁎ Native language not English −2.32⁎⁎⁎ −2.28⁎⁎⁎ −1.96⁎⁎⁎ −1.89⁎⁎⁎ Urban locality −0.55⁎⁎⁎ −0.56⁎⁎⁎ −0.91⁎⁎⁎ −0.91⁎⁎⁎ Rural locality −0.97⁎⁎⁎ −0.97⁎⁎⁎ −1.58⁎⁎⁎ −1.57⁎⁎⁎ Catholic school 2.13⁎⁎⁎ 2.15⁎⁎⁎ 0.86⁎⁎ 0.88⁎⁎ Other private school 3.85⁎⁎⁎ 3.84⁎⁎⁎ 4.89⁎⁎⁎ 4.88⁎⁎⁎ Divorce × sibship size (continuous) 0.26⁎⁎⁎ 0.41⁎⁎⁎ R2 0.14 0.14 0.14 0.14 N 19,806 19,806 19,803 19,803 ∗ p < 0.05. a All coefficients were weighted by the NELS base year weights. ⁎⁎ p < 0.01. ⁎⁎⁎ p < 0.001. Table options As shown in Model 1, adolescents from disrupted families score 1.03 and 2.09 points lower than peers in two-biological-parent families in reading and math tests respectively (p < 0.001), net of the effects of sibship size and other control variables. We also estimate the sizes of these two effects as −0.13 SD for reading 3 and −0.19 SD for math based on an equation for estimating adjusted effect sizes in regressions ( Keef and Roberts, 2004). These divorce effects are somewhat larger than the average of such effect on test performances reported in a prior meta-analysis ( Amato and Keith, 1991b). 4 In addition, prior research reports that such academic disadvantages among 8th graders in divorced families may increase during high school years ( Sun and Li, forthcoming) and may lead to low socioeconomic attainments in early adulthood ( Amato and Keith, 1991a and Sun and Li, 2008). Meanwhile, after effects of other covariates are held constant, each additional sibling is estimated to be associated with a decline around 0.52 points in both reading and math (the effect sizes are −0.07 SD for reading and −0.05 SD for math, p < 0.001). Overall, these findings on the inverse divorce and sibship-size effects are consistent with those documented in prior divorce and sibship-size studies. In light of these findings, we include in Model 1 the interaction term of parental disruption status × sibship size. As shown in Model 2, the main divorce effects on two performance measures are negative and highly significant, indicating that, net of other effects, only children (when sibship size = 0) in disrupted families respectively score 1.66 and 3.07 points lower in reading and math than only children in two-biological-parent families (the effect sizes are respectively −0.21 and −0.28 SD). Meanwhile, among adolescents in two-biological-parent families (i.e., when divorce status = 0), each additional sibling lowers adolescents’ reading and math performances by about 0.62 and 0.70 points respectively (or −0.08 SD for reading and −0.06 SD for math in effect size). More important to this study, both interaction effects are positive (0.26 points in reading and 0.41 points in math) and highly significant (p < 0.001). These findings suggest that, net of the effects of the controls, the inverse slopes of sibship size on both math and reading performances are significantly flatter in disrupted than in two-biological-parent families. Put differently, the negative effect of divorce on child performance is estimated to attenuate by 0.26 and 0.41 points respectively in reading and math with each additional sibling. It needs to be noted that although this interaction effect appears to be small (around 0.03 SD), its magnitude can cumulate to a modest level when sibship size increases substantially. 5.3. Differences in divorce effect by categorical measure of sibship size In the last section, the interaction effect of parental divorce and sibship size is assumed to be linear. To explore possible non-linear interaction patterns, we re-conduct OLS analyses and respectively regress reading and math scores on controls, parental divorce status, and the three dummy measures of sibship size: no sibling, three or four siblings, and five or more siblings. Adolescents with one or two siblings serve as the reference group, because in 1988 most American children under age 18 had one or two siblings (US Census Bureau, 1988). Table 4 summarizes these findings in Mode 1. We then include into Model 1 the three interaction terms of divorce × each of the three dummy sibship size variables (Model 2). To indicate statistical significance between adjusted performance means, superscripted A, B, and C are used next to the coefficient of each sibship-size category. Adjusted group means designated with different superscripted letters are statistically significant from one another at p < 0.05. Similarly, superscripted X and Y are used to indicate statistically significant (p < 0.05) differences in interaction effects. Because the coefficients of control variables are almost identical to those presented in Table 3, they are not reported in Table 4. Table 4. Unstandardized regression coefficients of regressions of adolescents’ academic performance on parental divorce status, sibship size (categorical), interactions, and parental resources. Independent variables Reading Math Model 1a,b Model 2a,b Model 3a,b Model 1a,b Model 2a,b Model 3a,b Intercept 28.29⁎⁎⁎ 28.39⁎⁎⁎ 17.55⁎⁎⁎ 39.75⁎⁎⁎ 39.89⁎⁎⁎ 23.96⁎⁎⁎ Parental divorce status −1.05⁎⁎⁎ −1.45⁎⁎⁎ 0.03 −2.08⁎⁎⁎ −2.64⁎⁎⁎ −0.21 Sibship size (categorical) Only childrenc 0.37A 0.25A 0.39A −0.07A −0.50∗∗∗,B −0.19A 1 or 2 siblings (reference)c 0.00A 0.00A 0.00A 0.00A 0.00A 0.00A 3 or 4 siblingsc −1.18⁎⁎⁎,B −1.38⁎⁎⁎,B −0.53⁎⁎,B −1.31⁎⁎⁎,B −1.47⁎⁎⁎,B −0.20A 5 or more siblingsc −2.00⁎⁎⁎,C −2.51⁎⁎⁎,C −0.67⁎⁎,B −2.35⁎⁎⁎,C −3.41⁎⁎⁎,C −0.65⁎,B Family income $10,000–$24,999 0.86⁎⁎⁎ 1.28⁎⁎⁎ $25,000–$49,999 1.59⁎⁎⁎ 2.22⁎⁎⁎ $50,000–$74,999 1.14⁎⁎⁎ 2.56⁎⁎⁎ $75,000 and up 1.27⁎⁎⁎ 3.73⁎⁎⁎ Money saved $1000–$5999 0.61⁎⁎⁎ 0.90⁎⁎⁎ $6000–$14,999 0.51⁎ 0.90⁎⁎ $15,000 and up 1.27⁎⁎⁎ 1.58⁎⁎⁎ Parental education attainment High school degree 1.00⁎⁎⁎ 1.26⁎⁎⁎ Some college 1.86⁎⁎⁎ 2.34⁎⁎⁎ College degree 3.62⁎⁎⁎ 5.20⁎⁎⁎ Graduate degree 5.69⁎⁎⁎ 8.33⁎⁎⁎ Parent occupational prestige 0.02⁎⁎⁎ 0.03⁎⁎⁎ Cultural classes 0.79⁎⁎⁎ 0.94⁎⁎⁎ Cultural activities 0.41⁎⁎⁎ 0.39⁎⁎⁎ Parent–child talk 0.91⁎⁎⁎ 1.16⁎⁎⁎ Attending school event 0.47⁎⁎⁎ 1.25⁎⁎⁎ Parent–school ties −0.09 −0.10 # of parents known −0.02 0.11⁎ Divorce × sibship size Divorce × only childrend 0.99X,Y 0.39X 1.35X,Y 0.44X Divorce × 1 or 2 siblingsd 0.00X 0.00X 0.00X 0.00X Divorce × 3 or 4 siblingsd 0.67⁎,Y 0.11X 0.61X −0.28X Divorce × 5 or 6 siblingsd 1.25⁎⁎,Y 0.17X 2.51⁎⁎⁎,Y 0.78Y R2 0.14 0.14 0.27 0.14 0.14 0.29 N 19,806 19,806 19,806 19,803 19,803 19,803 a All coefficients are weighted by the NELS base year weights. b Control variables in all three models include: students’ sex, race, disability status, native language, school location, and school type. c Adjusted mean differences in performance with different superscripted A, B, and C are statistically significant at p < 0.05 level. d Interaction effects with different superscripted X and Y are statistically significant at p < 0.05 level. ⁎ p < 0.05. ⁎⁎ p < 0.01. ⁎⁎⁎ p < 0.001. Table options As shown in Model 1, the effects of parental divorce are highly significant (−1.05 points for reading and −2.08 points for math). Except for adolescents with no siblings, adolescents in large sibship-size groups score significantly lower than peers in small sibship-size categories (e.g., the levels of reading and math performances are significantly lower among adolescents with five or more siblings than among their peers with three or four siblings, with p < 0.05, as showed by the different superscripted letters of B and C). In addition, adolescents with no siblings perform better than peers with three or more siblings (showed by different superscripted letters), but the performance levels between households with no siblings and one or two siblings are statistically non-significant. Overall, these findings are consistent with our earlier findings based on the continuous measure of sibship size, suggesting that parental divorce and large sibship size both have negative effects on adolescent performance. In Model 2, the main effects of parental divorce and large sibship-size categories remain statistically significant. More important to this study, the interaction effects show three patterns, with the first two observed among adolescents with at least one sibling. First, excluding the category of only children, the negative effects of divorce on both reading and math performances consistently attenuate as sibship size increases across the remaining three sibship-size categories. Among six possible pairs of group differences in divorce effect (three two-group comparisons × 2 test performance measures), four are statistically significant. The most striking differences are between adolescents with one or two (the reference group) and their peers with five or more siblings. Compared with the former group, the negative effects of divorce in the latter group are 1.25 and 2.51 points smaller for reading and math respectively (the effects sizes are 0.16 and 0.23 SD, p < 0.01). Between the category of one or two and that of three or four siblings, the negative effect of divorce on reading in the latter group is lower by 0.67 points (p < 0.05), although the same pattern of a smaller divorce effect in the latter group (by 0.61 points) is not statistically significant for math. Similarly, compared with that for peers with three or four siblings, the smaller divorce effect for adolescents with five or more siblings is statistically significant for math (as showed by superscripted X and Y), but not for reading (as showed by the same superscripted Y). It needs to be pointed out again that the two non-significant differences are still consistent with the overall pattern of small divorce effects in large sibship-size categories and are likely to reach a statistically significant level if the current sample contains more divorced cases in large sibship-size categories. Second, excluding the category of only children, the negative effect of divorce on adolescents’ reading performance attenuates almost linearly as sibship size increases by each category (e.g., from one or two siblings to three or four). For math, the negative effect of divorce first attenuates marginally from the one-or-two group to the three-or-four group (by 0.61 points) and then, substantially from the category of three or four siblings to that of five or more, revealing a trend of exponential decline. Finally, the divorce effects in only-child group are not significantly different from those in any of the other three sibship-size groups. This is likely to be caused by the unique performance pattern and the relatively limited number of divorced cases in one-child households. In summary, our analyses using a categorical sibship-size measure largely confirm the same pattern of interaction effects among adolescents with at least one sibling. Such interactions are particularly evident between families with one or two siblings and those with five or more. Overall, these findings are consistent with our earlier expectation for such interaction effects. 5.4. The intervening effects of parental resources If the levels of academic disadvantages in disrupted families decrease as sibship size increases, is this observed interaction effect attributable to variations in parental resources? To answer this question, we include all the parental resource measures (Model 3). Except for two social resource measures (parent–school ties and the number of parents known), all the remaining parental resource measures have a statistically significant and positive effect on both performance measures. These findings suggest that a high level of most parental resources indeed promote academic progress. With the inclusion of parental resource measures, the main effects of parental divorce are reduced to a statistically non-significant level. This suggests that in households with one or two siblings (the reference group), the negative effect of divorce on child performance is entirely due to variations in family resources.5 Similarly, the main effects of large sibship-size categories are also largely reduced, suggesting that in two-biological-parent families (when divorce status = 0), the negative effect of large sibship size is partially attributable to low resource levels in large families. More important to this study, when all resource measures are taken into consideration, the interaction effects of parental divorce and sibship-size categories are all reduced to non-significant levels. These findings are consistent with our earlier expectations, suggesting that the interaction effects between parental divorce and sibship size are completely due to the variations in parental resources among families with different divorce statuses and sibship sizes.