I would take a lot of that stuff with a grain of salt. There's someone in there claiming their AP human geography class didn't know what even numbers were. You really get the sense that there's a real creep in a lot of these stories from "I had a kid who did X..." to "My students do X...", all without any requirement to justify how some bad outcome is worse that it was in the past. teachers can be drama queens, and redditors can be idiots.

I'm sure there are districts in the US with dramatically under-resourced classrooms, but this has always been true. Right now there is a real zeitgeist where I live as well to try to tell this story that the kids are categorically worse as well, but honestly most of that is complete hash, or at the very best complicated. Covid did cause some general developmental delay and that is a real concern, but generally kids aren't much different than they used to be and in a lot of ways that are really important they're the best generation that's ever existed.