It's paid per child attending a state funded school in the area, not on per child existing in the area - and even it were to be changed, it wouldn't make that much difference because nobody knows for sure how many children live in an area.
Remember the stuff about 'Ghost children' post covid? That's because there is/are/were no complete records of children educated outside state schools.
Going by some of the posts here, I'm half expecting one of them to demand that their children are driven to school by people who have motorbility vehicles on the grounds the PIP is funded through taxation and it's not fair that somebody who has received money for mobility difficulties has then used it to lease a vehicle when the poor higher rate taxpayer's child has to make their own arrangements.