My son goes to church as well as weekly religion class. We let him break into it gradually. We found a children's liturgy program that he went to instead of mass until he had received his first communion. After that, he went to the children's program for half the mass, and mass for the last half. During that time my husband purchased a subscription to a magazine called MagnifiKid! which my son uses to follow along and read extra and interesting tidbits about the lesson. Now he attends mass full time with his MagnifiKid! in hand, and behaves really well. He doesn't exactly sit still, but he isn't disruptive, either. We sell it as extra cuddle time with mom and dad, since his favorite thing is to cuddle.
He actually enjoys religion, but he does have his own unique take on it, and I'm not sure what the priest would say if he heard it. But it works for him, and since faith is such an individual thing, I'm happy to leave it at that. We have some very, very interesting discussions.
He'll never be an alter boy, however. We discussed the idea, but he agreed that there was absolutely no way he could sit properly on the alter for as long as those kids need to.
So .... it rather depends on the child, the church, and many other things. There was a time when we thought we'd never be in church again, but things changed, and it's been really good.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).