Aha...that makes a difference. I understand what you are saying better now. I taught at the middle school level. We had 50 minute classes each day (6 periods total). I also agree STs should be required to stay on campus during normal school hours, but out district considered normal school hours to be roughly 7:30am-3:30pm. My CT often stayed until 4:00-4:30pm (especially on remediation day). I considered it my obligation to stay there until at least 3:30pm myself and often didn't leave until 4:00pm or later as well. I specifically mentioned in one of my first posts I was talking about STs (and teachers) that "try to beat the buses out of the parking lot" in the afternoon; ie, they head for their cars as soon as the last bell rings. Sometimes you have to leave that early, but not every day.