In school in England, the periods we studied in secondary school history class were pretty much just the world wars. In primary school we skipped over Roman and Egyptian history, Ancient Greek myths, and a little bit of the Tudors. There was a passing mention of Henry VIII founding the Church of England, but that was honestly pretty much it for Christianity in history class. We discussed Osiris more.
It’s quite possible that, at my very small school, the teacher opted to minimise the religion aspect as we had two Jehovah’s witness kids in a class of about 15 (the school had 28 pupils total), and she didn’t want to upset their parents by saying the wrong thing. I don’t recall Jesus being mentioned outside of school assembly, and a trip to the local church, which the aforementioned Jehovah’s witness kids were excused from. And that was in a Church of England school.
We did have separate Religious Studies class in secondary school, but many schools are able to choose their own curriculum for that, and parents can pull their kids out of it anyway.
Honestly, I could see someone getting through school in the UK without any mention of Jesus. I’ve even checked through the National curriculum requirements, and I’m pretty sure it could be done.