This study was to evaluate weight status and sociodemographic disparities in physical activity (PA) intensities (i.e., vigorous PA [VPA], moderate PA [MPA], and light PA [LPA]) during different segments of the school day, including physical education (PE), recess, and lunchtime. Participants were 287 third-grade students (Mage = 8.38, SD = 0.50). PA was measured using accelerometers. Children, on average, spent 88.48 minutes of MPA and 13.35 minutes of VPA. Disparities in VPA were observed in sex (higher in boys in PE and recess) and weight status (higher in the healthy-weight group in recess and lunchtime). Sex disparities in MPA were observed in recess (higher in girls) and in lunchtime (higher in boys). Hispanic girls had more LPA in PE compared with non-Hispanic girls. Disparities in PA behaviors at PE, recess, and lunchtime are evident but different regarding children's demographics. Schools may tailor PA opportunities to promote children's PA and reduce disparity.