University of Virginia Prof. Robert Pianta has a piece in the new edition of Education Next that says high quality teaching in pre-kindergarten can close achievement gaps between emotionally troubled children and the children of mothers with little education But Pianta writes that in the schools studied only about a quarter of the four-year-olds in the schools studied are lucky enough to get high quality instruction and emotional support. He also notes that just as in K-12, standard measures of teacher quality -- degrees and experience -- are not reliable proxies for quality and tend not to be consistently related to gains in achievement. So, he writes, classroom performance matters more than credentials and courses taken.