I have a theory about large bureaucracies. If they don't want to do something, they fail at it till it goes away.
I'll use schools as an example.
President W Bush supported a law that had schools tested, and checked on their ability to teach, and then have more funds given to those that did better. He also supported a system where parents could take their kids to those better schools as well.
The schools spent billions on making sure students passed these tests, and didn't actually teach better or find better methods to teach. Eventually it got so ridiculous, the entire thing was abandoned. The teachers won by failing.
Most states have requirements for each grade. Either the student shows they understand what is being taught, and can move on, or they have the equivalent time in hours, and are considered educated on the matter. Guess what schools do?
I took an online class in the 90's. It was so bad, I couldn't complete the first page because of a bug. Online schools continued to show they could do things, but most physical schools kept laws and directions to make it difficult for online schools to exist. Even today, during COVID, I know teachers that are angry that they have to teach online and have to deal with all of these rules, which they themselves made. They intend to make online schooling so bad, it fails and they win.
What other examples can you think of?
Sabotage has always been a tried and tested way to not obey your superiors. It goes back to Habsburg imperial officials: I obey, but do not execute.
As for the teachers though, I don't think it was as conscious as you say. It's all about incentives. If you make it possible to teach to the test, they will.
All the incentives in the world won't change the students you're working with, though. Barring any inherent genetic arguments, simply having students that were taught poorly early in their schooling will generally create persistent developmental issues. Tying funding to performance was a great way to start a negative feedback cycle.
There is a two part answer to this. A lot of schools receive more funding for students with learning problems. The second is creating a way to fix the initial mistake. This sounds like the two make a great solution, but they compete instead, and the school gets more money if the student remains unable to answer the questions or do the research.
True, if you can assess a learning disability, there's funding for that. If you can get a non-english student, there's funding for that. If you can get non-english migrant, it's a little gold mine. There are a lot of incentives to retard the learning environment.
And none to help anyone smart or gifted.