Boys have more trouble sitting still.
Boys seem to be hardwired for activity in a way that girls aren't. As a result, staying seated is a far more challenging task for a young boy than for a girl of the same age. In fact, half of 5-year-old boys are incapable of being attentive for more than a 20-minute stretch, according to Leonard Sax, M.D., Ph.D., author of Boys Adrift.
Boys also possess noticeably higher levels of dopamine, the chemical that helps direct both body motion and the flow of information within the brain. A study in the Journal of Abnormal Child Psychology suggests that movement improves boys' working memory, especially among those with ADHD. Male brains typically enter a period of minimal activity (known as a neural rest state) more often than female brains, so fidgeting and wiggling around may actually help boys learn.