To go back a rather a lot of posts...
The system of "choice" is a farce. It wastes huge amounts of everybody's time, whilst letting the middle-classes avoid confronting the social reasons (immigration, family breakdown, loss of social taboos that civilise behaviour) that give rise to so-called "bad-schools".
Everyone in the state sector should go to their local school, unless there is spare room at another school out of area. If it leads to the white middle-classes clearing out of London to the Home Counties (like the working class before them) then so be it.
Church schools funded by the state should have exactly the same admission criteria as "community" schools. RC schools are not especially sectarian (in England and Wales at least), but they do seem to be populated by the offspring of nominal left-footers who see themselves as ethnically a bit different. CofE secondary schools (and increasing primaries) are simply a dodge for filtering out the more undesirable elements.
If you want a specifically Christian school, do it privately, like this:
www.cfschool.org.uk/finance_fees.shtml
Ultimately though, I suspect where they are schooled makes little difference to the life outcome of one's children (or even their exam results). So this vast effort is to ensure that the "DC's" have a "happier" time at school. Which more than makes up for the house moves, entrance exams, stress over getting choices, tutoring, being split up from primary-school friends and goodness knows what else goes into the process.