Background: The innate ability for typically developing children to attain developmental motor milestones early in life has been a thoroughly researched area of inquiry. Nonetheless, as children grow and are required to perform more complex motor skills in order to experience success in physical activity and sport pursuits, the range of developmental abilities becomes increasingly variable. What is less known in the literature is if physical education and sport programmes deliberately designed to facilitate the motor development of these underlying abilities can improve the efficiency of purposeful movements in children. Purpose: To determine if the sensory-motor processing of lateral arm movements in children can be initiated quicker as a result of deliberate laterality practice. Participants and setting: Forty-five children (boys?=?23, girls?=?22), between the ages of 8 and 11 years, randomly selected from several Tasmanian (Australia) communities participated in this study. Each child participated in 1 day (~90 min) of data collection in a laboratory at the university. Research design: A repeated measures design using upper-extremity choice reaction time (RT) tests, separated by a 30-min treatment was employed in the current study. To test the effects of deliberate laterality practice on processing speed, children were randomly assigned into contralateral ball-bouncing (CBB), ipsilateral ball-bouncing, or a control video-game group (n?=?15 in each). The treatments were designed using tenants of Ericsson, Krampe, and Tesch-Romer's theory of deliberate practice on expert performance, and the specificity of the training principle commonly discussed in the exercise science literature. Data collection: On an individual basis, each participant performed 27 empirical trials of goal-directed aiming movements with each arm separately, during the pretest and post-test. The stimulus-response trials occurred randomly in three different directions at the same distance from the starting position (ipsilateral, contralateral, and midline). Data analysis: A 3 (treatment group)?×?2 (test)?×?2 (arm)?×?3 (direction) mixed design analysis of variance with repeated measures on the last three factors was used to test for significant differences, with an alpha level set at 0.05. Findings: Results revealed the CBB group experienced significantly shorter RTs in the contralateral direction during the post-test, likewise the ipsilateral group had significantly shorter RTs in the ipsilateral direction after the treatment. Further, the control group exhibited longer RTs in the contralateral direction compared to their pretest. Conclusions: Even after a short bout of deliberate laterality practice, children were able to reduce the processing speed associated with their lateral movements. Practitioners in the field may utilize these findings to foster developmental readiness in children wishing to improve their ability to perform the more complex motor skills requisite for successful sport and physical activity participation.