I went to an all-girls private school from 1977-1991. It was, at best, mediocre and, looking back on it now, positively shit in some ways. I can only think of one, maybe two teachers that genuinely inspired me. Most seemed to be marking time. Some were absolutely awful.
I coasted the whole way and was never pulled up on it, ever. I don't think they gave a damn, really. Most of us did go to university but I remember a very, very bright classmate being actively discouraged from applying to Oxbridge. I still see her and she still talks about it - she's angry about it, 25 years later. Careers advice mainly focused round the teacher/nurse/PA route.
The expectation that you would 'marry well' wasn't overtly expressed but it was there, definitely. The whole ethos of the place was set up for it. They never seemed particularly ambitious for us.
Subjects were the usual - english, history, geog, French or German, bit of Latin, art, textiles, maths, sciences - including the miserable Modular Science GSCE that I had to take because no one believed I could pass biology. I loved history but was told I was crap at it. We also did 'child development' and lots of cookery. I had elocution lessons, fgs. Sports facilities were...ok. A library that even I, at fifteen, knew was crap...but at least there was a library, I suppose.
I now have an MSc and teach at an RG university (precisely the kind of place that we would've been discouraged from applying to). I did well academically once I left - my education is mostly in spite of school not because of it.
Unsurprisingly the place went to the wall a few years ago. I don't feel that I was 'privileged' at all, really. If I'd been living in the 19th century and had had that education, maybe, but at the end of the 20th? It was a bit of a joke really.