If you want to understand the attempts by Catholic dioceses to prevent oversubscribed Catholic schools from using involvement in parishes rather than geography as a way of winnowing out who should attend, then take a deep breath and read an article in the current Tablet by Westminster's Director of Education, Paul Barber, entitled 'More Catholic than the Church'.
His argument is that all baptised Catholics have an (presumably equal, rather than absolute) right to Catholic education, and that Catholic schools should simply share them out by catchment area - isn't that the logical way of doing it?
One puzzling thing here is that, while practice varies, baptism itself is usually conferred only to the children of couples who show some kind of commitment to the Church. Being active in their parish would be an example of such commitment. So what the Barber doctrine says is that when a child presents him or herself to a Catholic school, the decision on admission should not be influenced by the parents' commitment to the parish NOW, but rather to their commitment five or ten years ago when the child was, or was not, baptised.
The bigger point however is that Barber is using exactly the same argument that was used twenty years ago to oppose Tory initiatives which allowed schools to compete with each other. People like teachers' unions said that when an oversubscribed school was allowed to cream off the brightest pupils with the most zealous parents other schools were damaged. The Tories replied that, just as with other forms of competition, when one school visibly drew ahead of others in terms of prestige, numbers, and funding, this would be an effective signal for the others to raise their game. Competition is a mechanism for spreading best practice - and indeed for developing the new best practice in the first place. The alternative is for bureaucrats to dream up 'best practice' in an office and impose is by fiat on schools - and that doesn't work.
It was an interesting argument, back in the 1980s and 1990s. Much ink was spilt. Government policy flowed one way, then another. But it's over now. The 'command and control' approach has been tested to destruction. No one seriously doubts the value of a degree of competition between schools. No one who expects to be taken seriously, anyway.
Or so I thought.