If you witness a crime, you are not required to report it. However, if it becomes known that you witnessed it, you can be compelled to testify in court. This doesn’t apply at all to this situation, but I’m saying it because people who might be in court one day in should understand it.

Again, the premise of applying this logic to this situation is incorrect. This isn’t a court, it’s a school. He has no legal rights protecting him from giving up a peer in this context (which means the school could and did expel him), and the correct rights for him to have in an ideal society wouldn’t be the ones granted by the American constitution. A school should be a place where children are nurtured and assisted by adults, not a mirror of a system of courts. The fact that this child was treated as a presumed criminal is a failure, which we can only compound by analyzing it with this legalistic framework. These children should not expect to be punished by default, and these adults should not punish them unless absolutely necessary.