Background: Children are encouraged to spend 60 min each day performing moderate-to-vigorous physical activity. In this study, we assessed the impact of an intervention throughout the school year on physical activity, sports performance, and school climate in fifth–sixth-grade children from schools in a disadvantaged neighborhood. Methods: The intervention group (n = 44) participated in six weekly 45 min physical education classes; an athletic subgroup of these students participated in two additional weekly athletic classes. The control group (n = 73) participated in two standard weekly physical education classes. Pre- and post-intervention Eurofit Physical Fitness Tests were conducted. Results: Significant improvements were seen in the stand-and-reach test among girls in the intervention group [M = −0.47(7.71)–1.26(8.02) cm] compared to the control group [F(1,54) = 14.86, p < 0.01, η2 = 0.22]. No differences were seen between the groups in their daily physical activity, screen time, or school climate (p = 0.13, p = 0.17, and p = 0.35, respectively). Improvements were seen in the shuttle-run beep test, yet only in the athletic subgroup [F(1,93) = 60.38, p < 0.001, η2 = 0.39]. A trend towards significance for the largest improvement was seen in the athletic subgroup, who participated in eight weekly physical activity classes [F(2,93) = 3.75, p = 0.027, η2 = 0.07). Conclusions: Physical education curricula should enhance their focus on athletic performance, while increasing the number of weekly physical education classes in schools, to include daily lessons throughout the school week, each lasting at least 45 min.