I like the idea of religions / belief systems / mythology being taught in schools without any religiosity. I went to a nondenominational school and we learned about all kinds of Religious belief systems, and also this included Humanistic (Jungianism etc) and Materialism: Scientism, Marxism in our "Religion" class.
I follow a Buddhist path and Dh is an Athiest, our Dd goes to a nondenominational private school - all state schools are Christian here (Ireland). There are plenty of different kinds of students and religions represented in our Dds school, but the fact remains that in effect Europe is Christendom, and their Winter Play - is called the Christmas play and it includes a nativity sequence.
I mention in passing to our DD some types of Buddhist practice at home, but nothing very much at this stage as she is only 4, and that's too young for any religious / belief system 'training' including Atheism, Marxism etc etc IMO.
Sometimes it does make me raise my eyebrow when DD comes home from her nondenominational school talking about the dead in Heaven, etc (There was one little catholic boy whose Granny had died, so he was talking to her about it)
I firmly believe that the ancient myths of Babylonia and Mesopotamia, the Scandinavian sagas and the Abrahamic religions have shaped Europe, the Levant and Northern Africa and its Diaspora (US, OZ, NZ, and colonies beyond), and these myth systems needs to be learned in school as a part of history, and civics as our systems of law and jurisprudence are derived from these.
The South American and African derived myths and major Religions are also very interesting and should be covered including the blood thirsty Aztec, Maya, Inca religions, Santeria (Voodoo crossed with Yoruba (Nigerian)), Kali, Animist, Paganism (Roman, Greek) Carthaginians (sacrifices to Baal and Moloch), Ancient Egyptian, Shamanism including (Tibetan)Bon and Wicca.
I agree that the public and private space divide must be maintained, and respect must be afforded to all, especially when we live cheek by jowel in urban areas distant and distinct from the countryside with its obvious seasons, and natural rhythms.
It's easy to fall into a huge debate about the intolerance of the major religion within any region, but we have to face facts that Europe is in effect Christendom and we live within that framework, and there is a huge emotional need in people to have ritual, and that includes having Saint Nicolas / Father Christmas / Father Frost, and other Good Will and neighbourliness Archetypes alive and kicking in the dark cold midwinter.
Here's a list by population of the religions of the world, with numbers of practitioners, for those who are interested