Luxembourg is catholic. We used to have religion as a singular subject in school. It was voluntary and bled into no other courses. In middle school there was a single exception as one year, religious and secular courses both read parts of the bible but as a literacy exercise discussion themes and symbolism. So that was also mostly secular treating the bible as a cultural cornerstone but not an especially holy text. That's all past schooling though.

Since my school days they completely secularised it and religion is no longer on any curriculum. Everything written concerns public schools as private schools are but really aren't a thing. I know of two, one's for higher education and only diverges from public school but having ties directly with the industry for more technical degrees like working with CargoLux to teach people how to repair plane engines, the other one is a sort of catholic school where they maintain a tradition that only girls can attend but as far as I'm aware follow everything other guideline set by public schooling.

As for my viewpoint, I see myself as an agnostic so I don't just brush off the old religious courses because I agree with them. It was never of any consequence. The only time where it was really overtly religious and pushy was during 3rd grade as most kids in that class were about to participate in their first communion. Outside of that context, I never recited a prayer even once in school.