I think this story provides a rational basis.
...
The teacher attempted to have the student suspended. The school in this case
did overturn that decision, but who's to say another school in a similar situation will do the same. It doesn't take the US to repeal the First Amendment for a teacher and a school who want to start enforcing this to do so haphazardly so long as the student involved either doesn't make a big issue or the parents don't sue.
The other issue is that there's quite a bit of subtlety in how this type of thing is enforced, for example, what constitutes "disruptive"? It's really up to the discretion of the teacher and school. I can see circumstances where what would be disruptive for a student who thinks homosexuality is immoral might not be the same as what would be disruptive for one with the opposite views. I have no doubt at all that someone somewhere will be punished along these lines.
To be honest, I'd suggest the right take a good long look at trying hardest to guarantee the right to dissent from popular sentiment on the morality of homosexuality rather than fighting over gay marriage. That ship has sailed; it really has. We need to make sure people are
allowed to view homosexuality (I'm taking the definition as homosexual acts, relationships, and fantasies btw) as immoral.