I have cut with schoolmates before, because they asked. I would go with them, skip a class and share a bathroom or hide somewhere with them. I didn't mind at the time because they didn't know I was severely depressed and it was a good opportunity to cut. I had to make sure I kept my cuts shallow though, so they didn't know how addicted and messed up I secretly was. My old mates were superficial, for attention cutters, whereas I was not.
I was caught once, by a senior student when I was in the bathroom during college. She pushed the door (which had a broken lock) and saw me bleeding just before I shoved the door closed again. Being a snitch, she made a fuss and tried to lecture me, then went off and told the deputy principal and the guidance counsellor. I was able to brush both of them off and get away without much trouble.