Whose religion do the kids practice?

When one parent is a different religion than the other parent, how do you decide which religion will be practiced by the children?

In our case, dad didn't disagree or raise a stink at all when the ex wanted to put the kids in parochial school or take them to her church even though it wasn't his religion. He left that up to her during her time since she acted ultra-religious (with two kids out of wedlock when the ultra-religious ex acted like the Virgin Mary, I found that a bit ironic but oh well). When she handed out first communion invitations, that was fine too. Her time, her choice as long as she didn't expect him to pay for the school or activities.  When we had my stepkids, he didn't take the kids to the ex's church on Sunday. The ex had to respect that as well.

It was too bad a family member of the ex's couldn't show a little respect. This person insulted my religious beliefs (not hubby's even though we share the same beliefs...she singled me out) and told my stepdaughter that I was going to hell because of them. Nice topic for a child.  If you are raising a child to believe in the fiery inferno of hell, you don't tell them somebody they love is going there (which means by extension so is their dad and siblings since we're all the same religion).

All these years later, the ex doesn't take the children to church anymore and parochial school didn't last long.  It seems the ex only felt strongly about her religion when her parents lived nearby and expected her to go.  When they moved a couple hours away, the ex stopped going to church.  Glad it was never a big deal like it can become in other families. It was a non-issue most of the time and a running joke at other times on the hypocrisy of some.