I always felt like when I played at another school, to be classy and not be an A$$ on their turf. we are the guests, and should be on good behavior. I also felt as the host when teams came in to play us, act like we have been there before. Win in a way that allows the other side to have some dignity.
My high school burned our school's logo into our rival's field before a game... they retaliated by stealing our "mascot" statue and replacing it with a plate of turds, we retaliated by stealing their statue and throwing it in the canal.
I guess now their statue has been thrown in the canal enough that they got a fiber glass one so it floats.
But the plate of turds probably wins.
They also whipped my school's butt probably 3/4ths of the time... so that is probably the bigger win.
At some point in the last 20 years the state did a total realignment of high school sports, they don't even play each other anymore, despite being only about 10 minutes apart and of equal enrollment sizes, but my school, Washington, was pretty ghetto and Sunnyslope just keeps getting pumped full of rich kids who should be going to Central High but their parents don't want to let their kids experience the real real so they get a variance.
Anyway, as long as no one gets hurt, I think a dirty rivalry is kinda fun.