I went to private schools including boarding school in the 80s. MrNC is a few years older and went to two comps in the 80s.
His schools had much better computer and tech facilities; mine had more sports and music space and equipment. Similar numbers of classes in portacabins or cold/leaking rooms, though my schools had some lovely architecture versus his post-war concrete. Similar numbers in most classes though some classes at my schools were very small (a single student did Ancient Greek GCSE).
Big difference in expectations - though if I'd been at state schools in my posh area of Surrey it would have been still different to his school in the Midlands - his home counties 6th form was more similar.
If you didn't get 5 grade A-Cs for GCSE you were kicked out at my school, though in reality anyone not expected to get at least 8 Cs minimum was pressured to leave well before that. MrNC learnt to read age 12 being severely dyslexic, but was in top maths and tech and physics sets, so a comp was perfect for him.
Everyone was expected to go to uni from my school, unless you went to art/nursing college or similar. I recall some students being shocked to hear in sixth form that lots of people - even the majority - didn't do A-levels let alone not go to university. I didn't know council housing existed until after I left school (there isn't any in my home town). MrNC didn't know private schools existed until he was in 6th form and his school liked aping one (he and brother refused to call teachers Sir after being on first name terms with teachers at their old school. The good teachers weren't fussed.)
My school had a lot of mucking about and a number of totally useless staff that would have had dire results in another school, but because we were all bright and expected by our families and other teachers to get good grades, after giving teachers grief we would go and do homework anyway and teach ourselves from the textbooks, so it wasn't obvious that I had no maths teaching from age 13 onwards and various subjects just had us giving teachers breakdowns.
The big difference was how savvy my schools were in dealing with the press. My school had regular fights on the school bus, resulting in bloodshed and one stabbing where the driver then beat up the sixthformer who did it then dumped him on the hard shoulder, older kids using drugs, but the only news stories that got out were the ice cream man being arrested for 'trying' to sell cocaine, and one rumoury piece about prefects using whips and knuckledusters to keep order. Ditto at my other school, staff getting girls pregnant, teachers getting sacked for being drunk and/or violent, a strippergram turning up - despite the local newspaper knowing all these, nothing was published - whereas a bit of jostling on the bus by local state school lads was made into a despairing "youth of today" article.
The flip side of high expectations is fear of not meeting them - anorexia and self-harm were rife, various suicide attempts, school psychiatrist was employed. And not knowing much about living on low incomes didn't help with that fear - total ignorance of the existence of benefits meant genuine fear of homelessness when parents lost jobs, and probably more parents with nervous breakdowns and going mad than you'd find in an average school. On the other hand, we gained a lot of knowledge of politics of various countries from kids whose families were expats or often in government there, and living in a boarding school sharing bedrooms really gives you familiarity with different cultures in a way that being neighbours or colleagues doesn't (again, my home town was 99% white, so really didn't do diversity). It was noticeable that close friends tended to have similar amounts of money or the wealthier ones would hide it.
MrNC and family had much more of a "the kids will be all right" attitude, so he got encouraged in the subjects he was good at by both home and school, and ignored his dyslexia totally.