Consider too that boys are very different from girls, both physically and emotionally. Boys are more physical and need to burn off some of that energy. It used to be that schools had recess at which times the girls often swang on swings while the boys climbed monkey bars. Kids would often work out their differences by getting into brawls ... but that's no longer allowed, either.
Since the sixties when feminists sought to balance and equalize the sexes, and environmentalists expressed concerned about exposure to certain materials, and school systems expanded the curriculum - boys are now expected to behave like girls, schoolyard swingsets and gym equipment have been scaled down or eliminated, and schools have reduced time spent at recess while increasing after school homework. (That's a long sentence but I think you get the point). Children today, especially the boys, are being denied the time they need to burn off their energy and simply enjoy their childhood. It's no wonder so many of them end up in the psychologist's office (another gift from the sixties).