Not for grades.
For dignity, for respect. In response to name calling, threats to sexual primacy over a girl (or boy). Some ethnic group taking over a table at lunch. Ethnic slurs. A push that was perceived as offensive, with a perceived need to restore honor--with the perceptions not necessarily those of the person who was pushed. "Did you see how that ____ pushed you? You gonna let him get away with that?"
Public displays of contempt and anger are approved of. Hey, can't hide our feelings. And they're culturally appropriate to young men 13 and older who are as far as they're concerned adults in everything but rights, knowledge, wisdom, experience, legal privileges, etc., etc. The only thing they're "adult" concerning is sperm production, but for them that's all that matters. This has a very strong correlation with SES, btw.
Yeah, there's competition. But charter schools come in several species. One is where parents put problem kids where there are rigorous behavioral norms--they show up angry, bitter, resentful, oppressed, at ages 15 and 16 they spout nonsense they've been taught by angry, bitter, resentful oppressed adults and their music. That's a serious culture clash.
For this, a lot of the increase in school violence tracks fairly closely the violence seen in low SES communities in the last couple of years. But we have to think of schools as isolated, separate. It's a foolish thing, but somebody has to do it to maintain karmic balance in the universe. I guess.
Another is warehousing. Where parents put problem kids so they can sit, drool, and get As for wiping their own asses to 75% mastery level at least 80% of the time. They graduate few because a lot of those kids transfer back to public school with glowing grades a month before the end of the school year. In time to miserably fail the final, putting teachers in horrible positions--have a large fail rate for students they didn't teach or simply pass them, knowing that their degree is pretty much worthless? That's if the course grade of A that transferred in doesn't average out with a final grade of 25/100 to above 70. It often does.
A third is where the geeks and nerds go to excel. Immersion Japanese, focus on STEM or performing or visual arts, etc.