I think this article in Vox covers some of the main points.

"...improving the American education system, while important, is neither a neglected cause nor a tractable one. It is a system on which hundreds of billions of dollars are spent annually by diffuse governments whose policies are difficult and expensive to change, where matters of importance are intensely contested, and where interest groups tend to fight each other to a standstill.

And it’s a system where, even after investing millions if not billions in research, we still don’t have a lot of confidence as to which interventions are helpful and which are not. The views of key actors, notably the Gates Foundation, have tended to shift rapidly on those substantive questions.

If every issue in the world were as crowded and hard to make progress on as education in the US, then I’d understand why foundations like Gates and Broad keep chugging. But that’s not the case..."

I realise this is not exactly the sort of answer you're looking for, but it's worth noting that EA priorities are meant to be in some sense the very most effective interventions in the world, so most things will not be EA priorities. As such I think it makes a lot more sense to place the burden of proof on people to prove that cause is highly effective, rather than on those who do not believe in the cause.