I notice a dissonance between "I don't trust that schools are doing much good", and "when you suspend students' schooling for a while, they still do well on standardised tests afterwards". What if the standardised tests aren't measuring anything useful?

I noticed this as well. It's pretty weird that Scott attacks the educational establishment so strongly and then seems to just give the standardized tests developed by and for this same establishment a pass without any scrutiny. And if there's one thing the public can agree on when it comes to educational policy it's that everybody thinks standardized tests are a hot garbage waste of time.