Too simplistic a question I think.
Church of Scotland: your children can’t come to this school!
Glasgow’s Catholic immigrant community: why not?
CoS: because you’re Catholics!
GCIC: oh, okay. Can we establish our own schools then?
CoS: if you must
GCIC: okay then
(years pass, Glasgow faith schools often outperform their ‘secular’ peers)
CoS: hey, why are you separating kids for primary school? Bigots!
GCIC: uhhh….
I can’t speak for faith schools in other cities, but in Glasgow you do not have to be Roman Catholic to attend a Catholic state school.
It’s also inaccurate to suggest that children educated at faith schools do not learn about other cultures and religions.
And as for private schools “not sucking much from the state” – who do you think has paid for the training and education of the majority of teachers employed in private schools?