What's an actually helpful teacher tip that you couldn't say in front of admin?

Mine is this -- at once a week I schedule an independent/group assignment lesson that requires <5 minutes of speaking on my part. Once the kids are set up to work, I go to my desk and get shit done. Grading, planning, responding to emails, stupid busywork, actually important work, etc.

A full period of independent work for them = basically a full day of independent work for me. Once a week, every week.

This way I never ever have to stay past contract hours. And honestly it's beneficial to the kids too because then I can plan great lessons for the other 4 days and they have a teacher who is happy/calm/not stressed. Win-win.