Charles Murray again writes what no one will want to hear:
Our ability to improve the academic accomplishment of students in the lower half of the distribution of intelligence is severely limited. It is a matter of ceilings. Suppose a girl in the 99th percentile of intelligence, corresponding to an IQ of 135, is getting a C in English. She is underachieving, and someone who sets out to raise her performance might be able to get a spectacular result. Now suppose the boy sitting behind her is getting a D, but his IQ is a bit below 100, at the 49th percentile.
We can hope to raise his grade. But teaching him more vocabulary words or drilling him on the parts of speech will not open up new vistas for him. It is not within his power to learn to follow an exposition written beyond a limited level of complexity, any more than it is within my power to follow a proof in the American Journal of Mathematics. In both cases, the problem is not that we have not been taught enough, but that we are not smart enough.
Now take the girl sitting across the aisle who is getting an F. She is at the 20th percentile of intelligence, which means she has an IQ of 88. If the grading is honest, it may not be possible to do more than give her an E for effort. Even if she is taught to read every bit as well as her intelligence permits, she still will be able to comprehend only simple written material. It is a good thing that she becomes functionally literate, and it will have an effect on the range of jobs she can hold. But still she will be confined to jobs that require minimal reading skills. She is just not smart enough to do more than that.
Having a low IQ doesn't mean you can't be a productive citizen. And if you think back to school days you can remember kids that just weren't cut out for book learning but they could rip apart an engine.
It's good for a society to value education but you don't have to go to college to be successful. Try hiring a handyman to fix some things around the house and you'll realize that he probably makes more than you if he's a hustler.
The problem with government education is that it won't be honest with itself about the limitations and expectations. Why not teach some kids vocational skills instead of trying to turn them into Voltaires?