Was going to ask you guys who out of the classroom teens you could and couldn't beat in a fist fight, but honestly, the only actual answer for "I would possibly lose to them" is Susie, so here's my list of "easiest" to "hardest":

Impossible to lose against: Snowy, MK, Temmie, Berdly, Kris
Really low chance to lose against: Catti, Noelle, Jockington
Might have a chance at all: Susie

Snowy and MK don't have hands. They're not winning shit.
Temmie might do something weird but you could probably punt her.
Berdly is Berdly.
Kris is that low because they don't have their knife, and even then I don't know how much having it would raise their changes.
Catti could scratch you and is a fatty but that's about it.
Noelle would easily be in the "Might have a chance at all" category if I didn't think she'd spend most of the fight terrified of actually throwing a punch, kick, or antler ramming you.
Jockington is a huge snake that plays sports. You could argue he has as much of a chance as MK and Snowy because he doesn't even have any limbs as well, but he could probably slither up your arms or legs and do something fucked up.

Susie is the only one here who might be an actual issue, but I don't know how tall or strong she actually is. Even then, she's not exactly in the best shape weight wise and if you had even a little bit of experience you would probably easily beat her ass.

So yeah, you could probably beat up a bunch of teenagers.