That's one of several interesting ideas outlined in this Washington Post op-ed by Mike Feinberg and Dave Levin, who cofounded the KIPP charter schools. They write:
[W]e should assess teachers on their demonstrated impact on student learning, not whether they hold a traditional teacher certifications. At KIPP, we have the ability to hire, fire and reward principals and teachers based on their students' progress and achievement. If we are going to hold all public schools accountable for their results -- and we should -- we need to grant this same power to all public schools. Otherwise, public schools will not meet the goal of providing a world-class education to every child.
We already test the students, and it works. Let's test the teachers too. I think we'd be shocked at the results.