Thanks, everyone. I ended up calling it the "Mathematician Award" and presented it with a little speech about how true mathematicians don't always have the correct answer right away, but they know that understanding _how_ to find the solution is as important as finding it, if not more so, etc.
I think it meant something to him. He had dropped out of the program early in the year for few weeks when he got discouraged about getting less than perfect papers, but he came back and finished out the year with us. I hope he thought it was worth it in the end.
