Educational research suggests that lower-income children exhibit poor general executive functioning relative to their higher-income peers. Meanwhile, sports psychology research suggests that an acute bout of aerobic exercise improves executive functioning in children. Yet, it has never been determined if such exercise (1) specifically improves the selective attention aspect of executive functioning in children or (2) impacts lower-income children any differently than higher-income children. The current study utilised a randomised experimental design and found that a 12 min session of aerobic exercise improved the selective attention of both lower- and higher-income children. Moreover, lower-income children exhibited even greater improvement than higher-income children. As the income-achievement gap persists, it is important to explore feasible interventions that strengthen the cognitive processes that underlie academic performance.