I’m not yet 50, but fortunately was educated before social promotion - by educated teachers who would fail and hold back students who hadn’t mastered certain objectives by year-end.
Sadly, those days are gone; the only requirement for high school diploma is attendance...
I am a few years past 50 and we didn’t have social promotion either. I remember in third grade, which was a big deal because it meant moving up to the bigger school down the street, our home room teacher called each students name and had them line up on the perimeter of the classroom in that order. Then she walked down the line and at a certain point used her forearm to cut the line and announced that everyone to the right would be going on to the fourth grade and those to the left would be repeating the third grade. Very public humiliation. Even then I thought that was harsh the way she did that but everyone of us kids were real clear that you earned your promotion (or you didn’t).
I think attendance as a criteria for diploma[s] went the way of the dodo bird. Now, I believe it depends on which protected class one finds themselves in. All others that are not in one of the protected classes have to earn their diploma.