That republican had stated during his campaign that he wanted to end the department of education…

Which I agree we should do, carefully. The federal government has no constitutional authorization to create educational standards for the country. Therefore, let those standards be set by the states.

What country with enviable educational results operates this way? Genuinely curious

Not sure where the UK stands on enviable results, but education is a devolved matter where the constituent countries can make independent decisions as opposed to there being a central government department that makes all decisions nationally.

Ok but which side supports it. Do you agree it’s a bad policy?

My point is that Democrats are implementing it by making classes worse for everyone.

Republican states aren't doing that. It's not the concept of No Child Left Behind that is bad, it's the implementation (and it's used as a reason to worsen classes).

Those states are declining too