As many have said before me, they crossed the line... If there were such suspicions, the first thing to do is contact the parents and the police. I do not know if they have the right to strip a person down in the school if there are suspicions but if that were the case then people could just blame others just for fun... If they do have such a right then I guess they would need some serious proof that she carries such pills.
Amidst the ruins of the ancient city I stand now baffled by the blazing battle fought in front of my bare eyes... oh man how much anime did I watch last night!