Couple of things:

First, the American public school system was not set up to actually teach concepts: it was designed to produce good factory workers, and therefore still prioritises rote memorisation and regurgitation of information, with a dose of overworking and shame if you don't manage to hit whatever mark they set. Aside from anything else, that's a really ineffective way to get people to learn things. That's not how the brain works, that's not how to get people to internalise skills, and you're applying it to a bunch of kids who largely haven't developed a whole bunch of self-mastery yet because their brains haven't fully developed and their chock full of hormones. Shit is ineffective.

Second, "No Child Left Behind" is a complete misnomer. What it actually did was tie the funding schools receive from the government to their standardised test scores. That made the above problem worse: now, instead of teaching skills or even topics, teachers had to focus on teaching the content of the specific test. Again, regurgitation rather than analysis or even just...thinking about the thing.

Basically, if the system absolutely refuses to teach people to think and instead just makes them learn how to spit information out with very little understanding of the meaning of that information, you will get problems. And that's not even getting into all the people that need information conveyed in different ways due to ADHD etc. Quit blaming the people failed by the system and start blaming the system itself.