This study investigated the physical activity (PA) levels of 6- to 8-year-old children over a seven-day period. The participants consisted of 35 girls and 36 boys in kindergarten and 113 girls and 131 boys in 1st grade. Physical activity (PA) is defined as “any body movement produced by skeletal muscles resulting in energy expenditure” and measured in this study using a Caltrac accelerometer. In addition to the data produced by the accelerometer, a detailed activity log was kept for each participant. The results revealed no statistically significant difference in PA levels between kindergarten and 1st-grade participants, F(1, 311) = 1.16, p = .282. However, boys were more physically active than girls F(1, 311) = 66.10, p < .001, ω2 = .06. Finally, the data on the children’s PA at school strongly supports the importance of physical education lessons (PE lessons) and recess periods in the daily school routine. © 2008 by the Association for Childhood Education International.