Yes and many of those DCs of hard working, but not so well paid parents (or parents like us where the Mum doesnt work and they have a big morgage) are the state schools top set A and A*s, in subjects they have the aptitude/perental support in.
Where state schools struggle and private schools are at a huge advantage is having the time and resorces to help DCs get good grades in things like MFL and English if they have technical parents or science when their parents are bright administrators.
At the DDs school Maths does pretty well, it's a well run dept. and they dole out loads of computer based practice. Science and particularly English have Ofsted breathing down their necks for lower ability pupils getting Cs. There is bugger all time and energy left to push an A to an A* or a safe B to a borderline A.
MFL get massively squeezed, short state school days and the timetable requirments of Maths, English and science to get ofsted acceptable marks leave them the very poor relation.
They always have been, outside the private sector. Even my grammar school, best uni in the country educated DH knows only a bit of French and a few wirds of German.