We know what the problem is. 8 years ago when my kid was in high School their math class had 45 students in it and there weren't even enough chairs for everybody to sit. This was not one of the poor school districts either. Not a rich School district but not poor by any measure. Meanwhile covid hit education like a brick.
On top of that parents are working two or three jobs just to keep a roof over their kids head.
We also don't allow public schools to abandon kids anymore and they're aren't any jobs for a high school dropout or frankly even a College dropout at this point. Certainly not something that you can make a living off of.
This means that you've got students who traditionally would have disappeared from the system but are now being educated and they bring the numbers down. Incidentally this is also why private schools look so good, if your grades start to drop in a private school they kick you out almost immediately. They aren't any better generally than public schools unless they have a lot more money and even then they can abandon anyone who isn't making the grade.
So basically a whole bunch of people we used to just toss into factory work can't do that work anymore because we either automated it away or we shipped it to china, and now those kids are still in the system and they are struggling and on top of that you have all the other social problems like covid and the leftovers from that and their parents not having any time because of over work etc etc.
There isn't actually a solution to any of this that doesn't involve massive transformations of society that a bunch of old farts like us are going to veto.
We could make the numbers go up and the class sizes go down by kicking all those kids to the curb but the problem with that obviously is we don't have anything to do with them and now they're just milling about getting into trouble. And we aren't going to do the kind of massive government programs Ala the New deal that would be required to employ that many people who struggle with high school algebra...
On the plus side the declining numbers and the increased cost of managing those kids means that we can point to how bad the numbers are and use that as an excuse to dismantle public education so I guess there is that. Think of all the tax savings for billionaires and all the profit when we privatize what's left of education.