First, there are a lot of things that go on at prom that are at least as contrary to Catholic doctrine as what this kid wants to do

Examples?

What about him bringing a male date actually violates their doctrine?

It would be condoning a relationship that is not acceptable according to their beliefs. Why allow them to let gay couples go to prom if they're not going to allow gay marriages in the church? It seems contradictory to accept same sex couples going to prom, only to reject recognition of their relationship in the future.

Third, it's very unlikely that the kid chose to go to this Catholic school, and I doubt he'd be there if he had the choice. I generally agree with your sentiment that you follow the basic rules and guidelines of places you choose to visit or attend, but in this case the kid's parents made that choice, not him.

I understand that, but it's certainly a tangent. The kids parents could also prohibit him taking the boyfriend to prom. The parents can make any kind of rules for the child that they want. This seems like an entirely different issue.

because it's what he is that causes the conflict, not who he's with.

This is simply untrue. Catholics accept the fact that gay people exist. You can be gay and be Catholic. It is the act of homosexuality that is not accepted. As long as you abstain from "the sin" you can be in the grace of God. There are plenty of out gay Catholics in the church. The teaching is that you should be practicing abstinence if you're unfortunate enough to have the inclination towards this particular sin. These beliefs are all very silly of course, but I'm trying to explain that they don't hate him only for the fact that he's gay.

But in my eyes, the moment those religious organizations wade into areas that aren't religious in nature (education, medical care, etc), they must compromise and accept that not everything that they do as a regular course of business is going to jive with their doctrines

You've made some great points, but this is by far the best in my opinion! Since Catholics are providing a private school that is a legitimate substitution for public education, they have to abide by the standards set by public schools. In order to provide an acceptable education to children, they must abide by the regulations set in place by our government. If this were a religious education course that took place in addition to regular schooling, I'd say they'd be in their right to forbid whatever they like. But since Catholics have offered their school as an alternative to public education, they have to play by the same rules.

Thank you, have a delta ∆ !