[jkeuhlen]

Because in addition to room/board/tuition, those at military academies are also paid a salary. It's above and beyond cost of schooling, and goes directly to the students instead of to defray education costs. I think that's the "direct" part of "no direct pay".

[wkrp]

You are not paid a salary while in a military academy, you are given a stipend from which they deduct food, board, and other costs.