Background: This study examined the volume and patterns of physical activity (PA) and sedentary time (ST) across different segments of the week among boys and girls. Methods: A total of 188 children aged 7–12 years wore a wrist-mounted ActiGraph GT3X+ accelerometer for 7 days. Time spent in PA and ST was calculated using ActiLife software. The mean number of minutes of light PA, moderate PA, vigorous PA, moderate-to-vigorous PA (MVPA), and ST were calculated per weekday (before school, during school, and after school) and per weekend day (morning and afternoon–evening). Results: After school represented the greatest accumulation of ST compared with before school and during school segments. Boys engaged in 225.4 min/day of ST (95% confidence interval (CI): 216–235), and girls engaged in 222.2 min/day of ST (95%CI: 213–231). During school, boys engaged in significantly more MVPA than girls (46.1 min/day (95%CI: 44–48) vs. 40.7 min/day (95%CI: 39–43)). Across the whole weekday, boys participated in significantly more MVPA than girls (103.9 min/day (95%CI: 99–109) vs. 95.7 min/day (95%CI: 90–101)). The weekend afternoon–evening segment represented the larger accumulation of ST, where boys were significantly more sedentary than girls (367.5 min/day (95%CI: 353–382) vs. 339.8 min/day (95%CI: 325–355), respectively). Conclusion: Our findings suggest that children are highly sedentary and spend little of their time in school in MVPA, especially girls. Routine breaks in school elicit increases in light PA and MVPA. Future work should consider the use of more active breaks within school time to encourage PA and reduce ST.