I'd expect this is one of biggest low hanging fruits in America today: how improving teaching craft would impact the students.
In many countries the way to get ahead in a school is to move into management. Mr Fryer says that American school districts “pay people in inverse proportion to the value they add”. District superintendents make more money than teachers although their impact on pupils’ lives is less. Singapore has a separate career track for teachers, so that the best do not leave the classroom. Australia may soon follow suit.