Sounds like one of our chemistry teachers who decided to help himself to chem store one open evening. ( He found key) We came in next day & started clearing up. There was a large conical flask with clear liquid in it, unlabelled. On closer inspection it looked a little 'oily'.
Turned out to be conc sulphuric that he'd got out for reasons known only to himself.
Needless to say key to chem store is taken away or well hidden on open evenings now.
Same teacher has also ; filled room with Lycopodium powder to point where kids are covering faces & breathing through their jackets.
Had kids standing on tables to watch him 'perform', kid fell off & broke ankle.
Set fire to floor, desk,, actually pretty much everything.
Lobbed large pieces of alkali metals into water & burnt ceiling. ( he still does this if he can get hands on key to flammables)
Blew hole in asbestos garage roof with Hydrogen balloons ( ties loads together) we had neighbours calling police on that one thinking it was bomb.
Drank dilute HCL in front of kids.
Broke door down to prep room when we locked it.
Other things too numerous to mention.
Perhaps @Emil Tac
could add to these stories!