I thought british public schools had to wear a uniform???
My town’s public schools (in NJ) have to wear a unifrom as well; they aren’t religious garb.
Generally, yes, most British state schools require children to wear a uniform. But a state school would be unlikely to be allowed to have a uniform that required students to wear extreme religious dress. A private school, however, generally could.
(note - 'Public School' has a very different meaning in the UK from its meaning in the US, so discussing these things can get confusing, but what Americans would call a public school is more often referred to as a state school in England and Wales)