I think that would be a great rule for Camden, but didn't know it had been discussed. By the council?
I did suggest a "no sibling" rule to Camden School For Girls governors, but was too late for the 2016 admission rounds. They say they will discuss for the next lot of admissions; while I am not holding my breath I think it's a positive that they will at least discuss.
Eleanor Palmer is in the news again this year as Giles Coren's daughter did not get in. Did you see his piece in Time Out? I don't know if the end of sibling rule would have helped them, they live close, but about the same distance as we do for the school and we were told we wouldn't have been given a place for the last ten years!
Anyway, back to the OP. Although there may be a shortage of places in CE, it seems there isn't anshortage in Haringey, Haringey have fulfilled their statutory duty to provide a school. I would personally go on the waiting list of all schools you would like, even those you wouldn't apply to inthe first place. If it helps I know plenty of children at religious schools who don't come from a religious background, or that of a different religion. They take part in the worship, may really get into it, but get their own thoughts in the end-well maybe parental power wins through.
Now, not meaning to upset northlondondad, but would the Free school at Whitehall Park be an option for you? If so it might be worth going on their waiting list too. Who knows what will happen there, it might be portacabins for years, it might.... Well who knows what it might. It's a risk I guesss, but only a parent can weigh up that risk.
If you are near Cambsbourne, could you get to the school on the other side of the park, the one near the big secondary school at AllY Pally station, walk through the park?
Sorry, it's rubbish I know. All the good things that come with loads of young children in a built up area have the school places as the downside. However the sort of area CE is, you may find that you bump up the waiting lists pretty fast as people don't want anything except Coleridge etc, so go private.
I'm not looking to going through it all again for secondary, although hopefully some people will have moved to leafy areas, and some will be saving their pennies for private secondaries.