What are we to make of articles (here [1] and here [2]) extolling IMPACT, Washington D.C.’s fledging teacher evaluation system, for how many “ineffective” teachers have been identified and fired, how many “highly effective” teachers rewarded? It’s hard to say, says David Cohen, John Dewey Collegiate Professor of Education and professor of public policy at the University of Michigan, for the Washington Post. I argue in my new book, Teaching and Its Predicaments [3](Harvard University) that fragmented school governance in the United States, coupled with the lack of coherent educational infrastructure, make it difficult either to broadly improve teaching and learning or to have valid knowledge of the extent of improvement…