It works like this: since would-be reformers can't control any of the variables in the education process BUT the teachers, the teachers must be the problem. Otherwise, the "reformers" can't actually change anything.
The teachers can't control the real variables, the reformers can't either.
This other point: the reformers HAVE NO IDEA how to improve teacher effectiveness. All they do is to place the RESPONSIBILITY on teachers to figure that out for themselves by measuring their effectiveness, though they don't know how to do that either. All the "reformers" are doing is to look for someone to blame for educational failure, without anything substantive to add to the conversation.
The problem is poverty, and all the associated conditions that go with it.
I teach in Montgomery County, Maryland. We are one of the best public school systems in the country, and have done more to narrow the achievement gap than any other system in the country. We are just north of the District of Columbia schools, some of the worst performing schools. I would point out that we are highly diverse in Montgomery, and have just become a majority minority county.
Some of the highest rated public school systems in the country are in the DC suburbs in Maryland and Virginia, also highly diverse. The top-rated high school in the country is in Fairfax County Schools.
What do we all have in common? Affluence. Five of the top ten income per capita counties in the entire US are in Maryland and Virginia, and most are DC suburbs.
But we can't talk about that. This subject is off the table in the modern "reform" movement. The idea that the teacher is the single most important factor in improvement is absurd in the lack of societal will to address the real factors that create a permanent underclass in this country.