https://www.sciencedaily.com/releases/2018/07/180712204421.htm

Study author Binwei Lu, of Durham University, used England's National Pupil Database to show how a child's chances of going to grammar school varied depending on the Local Authority (LA) in which they lived, their social and ethnic background, and their attainment level at primary school. The database included more than 600,000 pupils, of which around 186,000 were in the 36 LAs with grammar schools.

In those LAs, the proportion of pupils attending such schools varied widely: from 1.4 to 37.4 per cent. Selection criteria also varied, with pupils in certain LAs needing to achieve more than twice the Key Stage 2 marks of those in other LAs to have any chance of being admitted.