Lock the door or build a fence with locked gate to keep out the professors, mascots and cheerleader. The coach can still enter, but can be stopped by the visitor adjuster and he will still choose a sim to yell at, even if they're all fit. Long ago I switched the coach's fitness to fat, never saw him again. I'm not saying that will keep him away, it could just have been a coincidence. (:
When you forgive, you heal. When you let go, you grow.