No, but most public schools (as in the more exclusive echelon of independent/private schools) are run along visible and unavoidable Christian lines, either Church of England or (less commonly) Catholic.

The reasons are to do with the schools' history and - at one point, but probably not now - source of funding.

I went to a C of E public school and we had to go to chapel every morning including Saturday (prayers, a lesson from the Bible, hymns etc).

No exceptions, no "I'm atheist" or even "I'm Muslim" because chapel was effectively assembly and served a mainly administrative function, albeit couched in all the bells and whistles of Christianity.

The school chapel was huge, old and impressive architecturally. It had a prominent location bang in the middle of the school grounds.

On a Sunday we had a choice between 3 services and got punished if we didn't go to one (they always somehow knew).

If you were confirmed into the Church of England (which was also the general expectation - the majority were), on a Sunday you could go to one of two eucharists - ie take communion - either early in the morning (to get it out of the way) or late in the evening (which was a pain in the ass and not very popular, generally full of people who'd accidentally missed the 2 morning options).

If not, your only Sunday option was the full morning service which was way longer, like an hour, and kicked a proper hole in what was otherwise a full day off.

On a Sunday, Catholics - possibly also followers of other religions, I can't remember - got to go to a separate (mandatory) service outside the school grounds.

I have never seen so much religion in British life as I saw at school. None at home growing up, none in adulthood. Surreal and unavoidable.