Summarizing the material reviewed, we see that teachers matter and differ in effectiveness. The most important influence on individual differences in teacher effectiveness is teachers' general cognitive ability, followed by experience and content knowledge. Masters' degrees and accumulation of college credits have little effect, while specific coursework in the material to be taught is useful, particularly in more advanced subjects. Specific, curriculum-focused and reform-centered professional development appears to be important to effective instruction. Context studies tell us that all teachers can do a better job when supported by good curriculum, good schools, and good state policy. With the exception of the role of certification, these research findings align well with the provisions of ESEA.
There is an irony in demonstrating that teachers are important by showing that students' academic achievement is dependent on the teachers they are assigned. In other fields, substantially variation in performance among professionals delivering the same service is seen as a problem to be fixed. For example, we would not tolerate a system in which airline pilots varied appreciably in their ability to accomplish their tasks successfully, for who would want to be a passenger on the plane with the pilot who is at the 10th percentile on safe landings. Yet the American system of public education is built on what Richard Elmore has called the ethic of atomized teaching: autonomous teachers who close the doors to their classrooms and teach what they wish as they wish. The graphs from the value-added studies tell us what happens when a child has the back luck to be assigned to a teacher whose approach doesn't work. Variation in teacher effectiveness needs to be reduced substantially if our schools are going to perform at high levels.
There are three routes to that goal suggested by the research I have reviewed. First, we can be substantially more selective in the cognitive abilities that are required for entry into the teaching profession. Second, we can provide pre-service and in-service training that is more focused on the content that teachers will be delivering and the curriculum they will be using. Third, we can provide much better contexts for teachers to do their work. One important context is in the form of systems that link and align standards, curricula, assessment, and accountability. These policy directions are not conceptually incompatible, but each requires resources. We need better research to inform policy makers on the costs and benefits of each approach.
We are at the beginning of an exciting new period in teaching, one in which previous assumptions and ways of doing business will be questioned. As we build a solid research base on this topic, one that is more specific and experimental than we have currently, we should be much better able to provide effective instruction for all children. My hope and expectation is that when my sons have children in school they will not have to experience the anxieties nor engage in the machinations my wife and I went through each year as we tried to get our children assigned to what we believed were the best teachers in the next grade. Individual differences in teachers will never go away, but powerful instructional systems and new, effective forms of professional development should reduce those differences to the point that every teacher should be good enough so that no child is left behind.