Good idea. Both you do good and the students are happy. Both sides win from this situation. Perhaps you have caused a student to become acquainted with bitcoin at an early age. He will thank you later. I love that people around me do these things too. It's not something everyone is used to. Someone who does not know may look at this situation with surprise. Then the person who looks with surprise starts to learn. In every way, you make bitcoin and its environment win.