the answer is that they don't. To me the only way to justify it is if the kid is lazy and doesn't work hard either on the filed, in school, or both. If the kid isn't working then that is one thing but if he simply isn't as talented then that is not a justifiable reason. The coaches recruited and signed the kid because they evaluated him and felt he had the ability, that is on the coaches, so as long as the kid is working hard at both football and his class work then there is no justifiable reason fr the coaches to take away his scholarship.