The hard work they put into waking up early to go to their class, doing their homework, reviewing for their exams or recitation and just keeping up listening to their teachers' teachings are reasons to celebrate. Every student who passed should celebrate and give themselves a pat on their shoulder for a job well done.
Giving gifts to the graduates is something we need to consider, as it can be their reward. Ask your child what they want as much as possible if they want money, gift or whatever so they can truly appreciate what they receive. You can get them musiciansfriend.com dean guitars if they are keen on music, you can give them budget to spend time with friends like eat out, or buy a new gadget that they always dream.