Hiya!

From someone who's knee used to dislocated at least twice a year since I was 11........I would have wanted the teacher to put it back in!!!! The pain when it is out is undescribable!!!!! Depending on what type of teacher he was (P.E teacher etc) he might have been trained to do it. Its not hard to do, you literally hold the ankle, support the knee and pull the leg hard and it pops back in. I used to roll over the wrong way in bed and my knee would dislocate....it took until I was 16 and they thought my legs had "finished growing" for the to give me a knee reconstruction.

Hope he is ok xxx