I accept then that some C of E primary schools exercise selective admission criteria ...
I am pleased that you accept that Vlad.
but understand that some academy trust and free schools do to.
True, but outside of single sex schools, no school is legally permitted to discriminate on admissions on the basis of a protected characteristic, except faith schools. And even on sex there is a kind of tit-for-tat, so there are girls' schools that discriminate against boys and there are boys' schools which discriminate against girls. There is no equivalent for religious faith/lack of religious faith.
So if a non-faith academy school tried to do a kind of reverse discrimination - e.g. prioritising children who had not been baptised or requiring evidence that parents and their children did not attend church - then they be in legal hot-water before even you could scream "extreme secularists".
That all constitutes a problem to me.
I agree, but outside of single sex schools (and we can argue whether they are right or wrong) state-funded schools (indeed I think all schools) cannot discriminate on the basis of a protected characteristic, except faith schools.
Would it be fair then to say that you are more troubled by religious selection than the selection imposed by other schools.
No - I'm concerned with school-side social engineering of admissions in general (and parental side, but that's more tricky). But faith schools admissions is just in a league of its own, as there is no pedagogical argument that children learn better within a religious mono-culture.
Agree or not, there are reasonable arguments that boys and girls learn in different ways so a single sex approach can have pedagogical advantages. Also that students learn better within cohorts of broadly similar ability, which is the argument for selection. Now I absolutely oppose selective schools, and I'm not a great fan of single sex school, not least because I think you can retain the pedagogical advantage without actually segregating the pupils into different schools. But there is, at least, a pedagogical argument, which simply isn't there for faith schools, which is basically just state-funded discriminatory social engineering.
Since to me selection of kids in terms of parental cash or academic ability seem more cynical than religious selection.
But in fundamental equalities terms, society doesn't agree - as religion, or lack thereof, is a protected characteristic. Amount of money we have isn't a protected characteristic, and nor is academic (or other) ability.