The kids are typically high performing. The teachers feed off of that and encourage it.
It's sliding and down-in-the-dumps schools that need them. Othewise it's easy to spend more and more time teaching less and less. Until finally you have schools that don't really teach much.
Which is why the original tests were introduced. They were basic. Can you read OTC medicine instructions? Can you read a simple map? Can you manage to master the math for balancing a checkbook? Can you read simple narrative and non-fiction prose for information?
Now we have "essential skills and knowledge" that are anything but. I know students learning about quantum states as sophomores and n-numbers for calculation electron transitions. This is considered "essential knowledge." Odd, I seem to go most of my year without once worrying about such things. I find them interesting; I liked learning about them; I can talk people through Planck's solution to the UV catastrophe and teach the math at at least the jr-year college physics level behind Bohr and de Broglie's advances. Still ... Doesn't seem like "essential knowledge."