Back in 7th grade I stumbled upon the "net send" command. So, bored in the back of class one day, I sent a few messages and saw them pop up simultaneously on all the computers. I thought it was pretty funny. I didn't sent anything vulgar. Just something like, "yo", and "it's Evan" (yes, I put my name).
Well, turns out I sent those messages to every computer in the district. Three elementary schools, one middle school, one high school, and the administration building.
Maybe 10m later someone from the IT team came and asked who had computer #XX. Obviously was me. Principal claimed I hacked into all the computers and said he'd call me back in for an appropriate punishment.
Nothing ever amounted to it. Never got called back in so I had no repercussions.