"stay with the RE curriculum. Which is about all faiths, unless the school is unusually bad."
DD went to a community primary school, NOT a faith school. There was (according to her, but since everyone else I know & have spoken to about the subject has heard the same thing I have no reason to disbelieve her) effectively no teaching about other religions than Christianity. They said prayers three times a day: in assembly, at lunchtime, and at going home time. They had one week in yr 5/6 (mixed class) where the entirety of every afternoon was given over to a Bible studies course taught by an evangelical christian group that came into the school. Every child was given a hard back illustrated bible. I could go on, but you get the picture. There was no other realistic option - the next nearest primary (6 miles) shares a head teacher with dd's old school, the next again is equally religious.
Even in secondary, when Gideon bibles were given out there was no option to avoid it - not like when I was in secondary where it was 'those who want one go to this side of the hall, those who don't go to the other side.
Short of moving to a city, in large swathes of the country, this is the norm. As it happens, it doesn't bother me greatly beyond the waste of time, when we're told that many many things 'can't be fitted in' because of the constraints of curriculum time. But given that the last British Social Attitudes survey found that 51% of the population said they had 'no religion' compared to 42% who said they were Christian, it's not surprising some people are unimpressed. (FWIW it's not that we're in a particularly religious area, DD's now in secondary, apparantly when here RS class were asked if any of them went to church, one boy said his family 'went occasionally' - that was it.)