In the US it's driven by the fear of breakdown in church/state division-----a fear which I feel is vastly overrated--but, interestingly enough, seems to be shared by many Mudcatters.
And in fact, as is illustrated here, this attempt to purge all traces of religion from public life has caused a strong reaction on the other side--and plays into the sense of the so-called Religious Right that THEY are under attack..
So both the "Religious Right" and those who reject organized religion feel under siege by the other--truly a spectacular achievement.
But I suspect that those of us in the middle would be glad to take Mao's advice and "Let 1,000 flowers bloom"---including in the schools.