Study: Video games cut into children's study time
When kids play video games on school days, boys spend 30% less time reading and girls spend 34% less time on their homework, compared to kids who did not play video games. Gaming did not cut into time kids spent with family and friends.
Hope M. Cummings, H., & Vandewater, E. (2007). Relation of Adolescent Video Game Play to Time Spent in Other Activities. Archives of Pediatric and Adolescent Medicine, 161, 684 - 689.