Germany's really awful on this front. It's one of these things (like church taxes) that seem very odd and strange in a comparably secular country like Germany, but schools in almost every state (Berlin's an exception, I think) offer "Catholic" and "Protestant" religion classes, sometimes even by a priest in a public school.
You don't have to attend these classes, as usually an alternative "ethics" is offered....but it's still something that really does need to go...
That doesn't really surprise me since Germany doesn't have true church/state separation, with that church tax funding thing.
One thing I've wondered, if your parents register you under a certain church, do you always stay registered under that upon becoming an adult unless you specifically go through the process to de-register, or is it something you have to continuously re-register as? I know not making any church donations through the state simply requires checking the box to not do so on your tax form, but I'm not sure about being registered to a church in general.