LA gang member shoots guy over graffitti (Solved)

I always thought this was "The Principle" , and maybe there is some school element involved, but i watched The Principle the other day and this didnt happen.

The scene i'm thinking of couple of gangbangers are walking down/across the weird concrete LA river, and find some dude disrespecting their graffitti with his own.

Needless to say the guy ends up shot dead , the gangbangers ankle tag beeper goes off (cos he crossed the river maybe?) and moans he'll have to explain to parole officer / teacher whatever


I seem to remember the teacher going really rogue , more than in 'the principle' so maybe thats this movie too