Most schools have lists of must-haves for children going to them that parents have to buy. A lot of companies take advantage of that and jack up the price of those items. There are also a lot of those things that parents have to buy multiples of at the beginning of the year and hand over to the teacher for the student to have access to over the next 9 months.
Yeah, it's thanks to continual defining of our public schools in order to funnel money to religious and charter schools as well as private schools via voucher programs.