I agree with what you've said, and my initial thought was there are many varieties of grad school with night class, executive MBAs etc so it would be simpler to exclude it. I also should change the Undergrad to full time UGrad.
If someone is a full time Grad student going for something like their PhD in something and eating ramen 3 or more nights a week you might just qualify, but many grad students I know also live quite well, so it is a bit of a 50-50 split.
I may remove the high school category, but I know that I mostly funded my own hobby while I started with birthday and christmas money as well as random jobs, and other things, so I know that money can be tight for younger people. Plus the fact that it is an unusual hobby and the prices are not understood by most people. With that said, that is why I tried to distinguish it is for STUDENTS not their parents. So if the paypal account is their parent's money I may refund them and say this voids the policy. With that said under 18 you can't have a paypal account so it is a bit complicated...
With that said, I'll see how it works and tune it so it works the best it can and isn't taken advantage of completely. I may only do this randomly a few times a year, I'm not sure yet. Right now I'm going to see what happens as the weekend comes and go from there.