The lab admin had disabled Ctrl+C and Ctrl+Break to keep folks from breaking out of the DOS-based login prompt to a C:\ prompt, but I somehow figured out that Alt+3 passed an equivalent character and had the same effect.
I once got yelled at for being “in the lab too much” by one of the teachers, but I never got in any trouble. I suspect the lab admin (a kind older programming and math teacher) knew what we were up to.