When I was 11 or 12 we had a bunch of old Windows (2000?) boxes with a shared network folder — all the students' files were in the same folder. I had just learned about basic batch file "programming" so I made one called Change Your Grades Click Here!!.bat which asked for your username and password (we had individual accounts on the Mac computers) and saved them to a hidden text file in the same folder. Most people didn't fall for it, but I got one girl's login that actually worked, which scared the shit out of me, and I deleted the program. (I really wanted to tell her that "emma" is not a good password, but I thought it wouldn't turn out well for me.)

A few years later, I cracked the admin password (with a Ophcrack live USB) for a silly reason: they had the machines mostly locked down, and I wanted to change the desktop background hahah. I remember being quite disappointed in the sysadmins that the admin password for all the machines in school was a common dictionary word, cracked in 30 seconds.

Oh, once I met a guy who identified as a "hacker" (in the sense of breaking into systems illegally) and he told me (then a young teen) to "have my fun" before I turned 18 and then to stop, which in retrospect was very good advice.