I never had a single teacher actually give standards for papers until like halfway through college. But part of that is probably because I was still on the cusp of people writing papers on a computer in the first place when I was in school.
I mean, when I was in elementary school, you'd have been doing your homework on an Apple IIe and printing it out on a dot matrix printer. Even by college, neither Google nor Wikipedia existed yet, and even the more advanced students would only have Windows 95, while most of us still had Windows 3.1 (and one of my roommates in college was using still OS/2). Standards take time to develop before they become more or less universal - for a while, teachers were still figuring out just what computers were capable of, and the best ways to use them.
But I definitely remember times when a teacher either asked for 10pt or single-spaced. Mostly because clever people would exploit kerning and spacing to put less content in an assignment than the teacher expected. I'm not sure there was ever really anything resembling a standard expectation even by the time I graduated (there was also disagreement on the best way to cite - teachers tended to lean more towards the Chicago Manual in high school, but my college tended to favor MLA and APA depending on the teacher).
My first papers for school were typed at home on a typewriter. I have no idea what the font size is or format. I didn't type a paper on a computer for the first time until 1993 and that was at my school when I was 13.
The format? You guessed it: Double spaced, New Times Roman. Maybe it depends on the state and how "important" the dept of education thinks it is?