I see it as a very big deal.
If you were to go in to the school and hand out a colour in sheet on atheism or even just agnostics...it would be seen as the worst devil spawn thing.
It is just as bad on the other side.
I would make a complaint to the department of education as it seems this school cannot follow a simple request.
It is discrimination as you can bet your bottom dollar that the religious would get any sort of atheist evangelism, shut down, pronto!