"Grading" is going to be very difficult for such a subjective topic.
The ability to share a collection in order to excite the audience is very important. They must know their collection AND be able to explain its historical significance.
Get some other judges to help you out: someone from the media and someone from the performing arts community.
Consider giving gift certificates to the students. Accepting cash may be a potential issue in the future for some of these kids.
- For Teachers