Whilst we all seek to nurture young student SMs and harness "raw talent", there must be clear guidelines for acceptable behavior, the most important being safety. In order to deal with a problem worker, there needs to be discipline. No one can be afraid to say to him "don't do that," and to punish him when he does it again. As much as you can, define the problem as one of behavior and not one of emotion. As others have mentioned, you can alter behavior and actions more than you can adjust attitudes. People often turn away or isolate the problem person because we might not want to create more conflict by confronting him. And by confronting I don't mean shouting - just setting clear definitions of un/acceptable behavior. When they mess up, tell them, and when they mess up enough, say goodbye. When you deal with problem situations directly, you are also respecting the problem person by giving them a chance to do better by giving clear directives on how to improve their behavior and performance. And if you need to let them go, they'll know why. But your reasons must always be good and clear ones, especially in the tumultuous arena of student theatre.