wayyy back in Gr 9 my gf and i used to fool around on the Math teachers desk while she was out for lunch. another student walked in on us, told everyone, word got around so we figured we'd play it safe and not do it again. not really "caught," but that teacher wasn't really nice to me ever again.
8th grade I was fingering an ex in the girls restroom and a teacher walked in and yelled at us but nothing bad happened. Then in 9th grade, i got an hj while watching some movie. We just put a coat over and the teacher just smiled and winked at me. She loved me so she wouldn't cock block me.