America's education system is based on the assumption that barring illness or an extraordinary event, students are in class every weekday. So strong is this assumption that it is not even measured. It is the rare state education department, school district, or principal that can tell one how many students have missed 10% or more of the school year…

School districts, individual schools, and education policies all contribute to student achievement. But it can be argued that the most important contributing factor is the quality of the teacher in the classroom. Evaluating teacher quality is complicated, yet it has become even more important with the testing and assessment focus of No Child Left…