I do not have any recollections of teachers correcting my grammar, that doesn’t mean it didn’t happen but I just don’t recall any (it was 40 years ago). I do have many memories of family correcting my grammar. ‘Ain’t’ was not a word to say around my mother. Once when I told her, “I ain’t got homework” she said I obviously didn’t study enough if I was saying “ain’t” as it wasn’t a word. I was told to go read a book instead of watch tv (the horror). My Aunt Jane was terrifying if she had to correct your writing or speech. Whatever was said ‘improperly’ was corrected with a lecture followed by being told I sounded uneducated and needed to speak English properly in life if I wanted to get ahead. (I had a habit of asking if I could ‘borrow’ her bathroom instead of saying ‘use’ the bathroom.) Of course my two older sisters weren’t as nice, and they would correct any perceived grammatical error by laughing and saying I sounded like an idiot (I’m pretty sure I said “ain’t” in some sentences to them). To this day I can not seem to remember the rule concerning ‘I’ vs ‘Me’ and will just spit out several options and let the listener choose their preference and kind of hide the fact I’m not confident in the correct way to say it. So although I am sure there was a prescriptivism structure of teaching grammar in school when I was growing up, most of the corrections were made and enforced at home. And today at the age of 55, I am still scolded by my mother if I use some choice words even if I am describing my boss on a bad day at work. Her reasoning is that it sounds uneducated if I curse a lot.