The childhood obesity epidemic has motivated the implementation of physical activity (PA) intervention programs. The aim of this study was to determine the effect of an educational intervention program on the pattern and knowledge of physical activity in 6 – 8 year old school children in northern Mexico. A randomly controlled clinical design was employed, involving 6 elementary schools: 3 schools running the intervention program (n = 80) and 3 controls (n = 79). Anthropometry (weight, height and BMI/age) was evaluated, and the type and frequency of weekly practice of PA was recorded before and after the intervention. Anthropometric measurements were similar among all the groups at the beginning of the program. Children assigned to the intervention not only improved their knowledge about recreational PA (p = 0.03) but also increased their practice of walking (+23%), dancing (+19%), and playing soccer (+19%), (p ≤ 0.05). The educational program had a positive effect on participation and knowledge of the recreational activities of children.