Preppies Vandalized glitchScrewing around one day and I found this. Just proceed with the mission as normal. Once you get back to the boxing gym, attempt to get Derby to follow you. Just be careful not to get too close to him or the mission will end.
I haven't taken him anywhere else but the auto shop. I know this won't work at the so called "driveway" to the school parking lot. Having other students attack him won't end the mission. If Derby is knocked out by another student or busted, the mission won't end but you won't be able to do this glitch. When you attack him at the shop, the mission will end and you'll be back at the boxing gym. The cutscene plays normally, but after that...
Well, it was a little bit boring here. Normally Jimmy teleports all over the place. It's pretty funny.