While I tend to agree this may be a bad situation I think you are taking gigantic leap to conclusions with this and painting with a an exceptionally broad brush.
Given the number of actual teacher/coach predator abuse reports, slinging mud at essentially volunteer coaches is a pretty unnecessary thing to do. Particularly to a specific situation that you have no details about.
And how do you know the school is not conducting these background checks on volunteers?
Yes, I think the cases of scoundrel HS coaches who are bias and unfair is far more prevalent than predator cases. In fact, I think the predator cases are extremely rare given how schools are so (justifiably) sensitive to it.