This study examined the psychometric properties of motor praxis using a large school-based sample of children (n = 239). We developed and evaluated the construct validity of a motor praxis assessment using confirmatory factor analysis (CFA). A model with four latent variables was evaluated for goodness of fit. CFA established that the scale was multifactorial and supported the four-factor model (motor imagery, verbal gesture production, imitative gesture production and knowledge of object-use). The internal consistency, inter-rater reliability and concurrent validity of the praxis assessment mostly demonstrated good to excellent results for the full scale and the subscales. The motor praxis demonstrated an ontogenic progression in 6-, 7- and 8-year-olds, suggesting a developmental trend during these ages, but with the exception of gestural representation on imitation. Implications for motor development and clinical evaluation are discussed herein in relation to the four instruments.