How much do your kids contribute to back-to-school expenses?

Now that August has arrived, I'm starting to get the kids ready for going back to school. I'm trying to get them to bed earlier. I'm nagging them to finish their summer reading assignments. And I have the 11-year-old practicing his multiplication and division.

The kids are whining that I'm being too mean, but they don't know how easy they have it. I read a recent report from the National Retail Federation that says the average 13-to-17-year old will spend $36.48 on pens, papers, lunch boxes, etc. as they get ready for school. The younger kids (6-12) will spend an average of $25.63 on what they want for school.

Seriously? Do parents really make their kids buy their own pencils and paper? For my kids, going back to school is painful enough as it is. I can't imagine what they would say if I told them they will have to buy their own school supplies this year.

Am I spoiling my kids? Do you make your kids contribute to their back-to-school purchases?