This was around 1993 or 1994 and I was in 11th grade. I was in some fairly "bonehead" computer class and we often worked on simple projects and saved them to floppy disks to take home or work on later.

At the time, the family computer was still an aging Commodore 128 but I was working mostly in DOS at school so I'd bring home my disks and work on projects on my dad's work laptop. Dad's work laptop included a primitive virus scanner so of course I scanned the disk I'd been using on the school network. The scanner finds some minor virus and cleans it up (in retrospect, I guess it could've easily just been a false positive but who knows).

After taking the disk back to school and working on projects again, I scanned it at home the following evening. Virus once again detected. So the next day in class I mention to the teacher that there's probably some innocuous virus on the classroom network and offered to help get rid of it. I was interested in that stuff even if I was still mostly a novice.

But instead of giving me a new project, the teacher flipped out. She accused me of trying to start a panic and disrupting class and sent me to see the ass. principal. Now, this dude hated kids (especially the ones who clearly had no respect for authoritah). I had to sit in his office without speaking while he held a (no joke) half hour conversation on the phone with his friend about some fishing trip they had planned for the weekend. Afterward he reamed me out and basically told me I was full of shit because the teacher wouldn't lie about such things.

In the end, it was my first lesson in "people who don't get computers or trust them will often avoid dealing with issues that make them uncomfortable and possibly view you with hostility for suggesting otherwise."