The cost of a bad teacher

Eric Hanushek in the NY Times writes:

A small percentage of teachers inflicts disproportionate harm on children. Each year a grossly ineffective teacher continues in the classroom reduces the future earnings of the class by thousands of dollars by dramatically lowering the college chances and employment opportunities of students. 

There is also a national impact. The future economic well being of the United States is entirely dependent on the skills of our population. Replacing the poorest performing 5 to 8 percent of teachers with an average teacher would, by my calculations, yield improved productivity and growth that amounts to trillions of dollars. 

Protecting bad teachers has a massive impact on students. and through them the country. we should pay our best teachers more, and move on those teachers who are not skilled in connecting with students/