At the age of 13, what was HIS reaction when asked to participate? Did the teacher force him to do it with threat of punishment, or ask him and he agreed? I would want the full story before jumping to any conclusions.
He's a rather docile kid and so if a teacher says he has to do it, he does it.
Its one of those slippery slope things. You teach kids to respect authority but as they get older you also want them to begin to question authority especially if it is not in their best interest. Finding a happy medium is hard to teach.