Labor unions can be a force for good, especially in protecting the interest of workers against exploitation. But as with any human institution, unions can become harmful to the common good. That is particularly true with teachers unions, which often promote the self-interests of their members even when they are antithetical to the interests of students.
In this 5 minute video, Terry Moe, Professor of Political Science at Stanford University, outlines the problem of teachers unions and offers solutions to how it can be fixed.