Sorry for dragging up and old thread however some simple legal definitions can resolve the OP's issues. This is about peoples opinion. The question is looking for legal clarification:
"Education expenses are tuition and fees required for the enrollment or attendance of a student at an eligible educational institution, and expenses for fees, books, supplies, and equipment required for courses of instruction at an eligible educational institution".
"Child maintenance is money paid by the paying parent to the receiving parent towards their child’s everyday living".
Therefore socks and underpants are not educational expenses and are covered by the child maintenance he is paying every week.