Over at Charter Insights, Doug Hering has written a post about teacher evaluation. He briefly mentions a point that should be emphasized: teachers should be measured on how well their students are learning and if the students aren't learning, it's the teacher--not the student--who needs to adjust. Frequent assessment, both formative and summative, should be examined. There should be multiple measures for what, and how well, the student is learning.
Charter schools have the freedom to hire teachers on an at-will basis and don't negotiate with the teacher's union. This means they can hire the very best teachers, which is ultimately a key factor.
There are a few really top-notch charter schools that require candidates for teaching positions to teach a mock lesson in front of students. This feature of the hiring process shows if the teacher has rapport with students and what type of classroom management skills the teacher has. This hiring practice has enabled some charter schools to make excellent hiring decisions, which result in fewer dismissals or lack of academic performance during the school year.