Chayecha kodmin l’chayei chaveircha
FTFY
That means your life comes before someone else’s life. It doesn’t mean that your kid listening to rolling stones comes before someone else going OTD.
I am not aware of any yeshivos which routinely kick kids out “all the time”. In the rare cases where kids are kicked out, the negative influence is usually karov l’vaday. Perhaps you are, and then they’re wrong.
Sure, karov l’vaday. Of what? That the kids in the class will all go OTD? Unlikely. That some of the other kids might also listen to goyish music? Big deal. You’re killing kids over that.