Well no surprise at all.
However the schools in poor areas likewise fail rich pupils.
The schools in poor areas will concentrate on passing Maths and English GCSE, because if you pass those then you just need to add a vocational qualification or two, which are comparatively far, far easier, to tick the '5 A*-C at GCSE including Maths + English' box.
Schools are understandably focused on the needs of the bulk of their students.
The difference is that a middle class child who doesn't do Ebacc, doesn't go on to do academic A Levels, gets a mediocre set of GCSE passes and so on, won't show up in the same way as a deprived child who goes to a school where they aren't focused on the needs of children who will struggle to scrape two Cs at GCSE and an NVQ in Sports and Applied Science.
Basically a lot of comprehensive schools are secondary moderns in all but name.