L.A. teacher ratings: L.A. Times analysis rates teachers' effectiveness - latimes.com:
An extensive value-added analysis of teacher effectiveness using student performance results in elementary schools in Los Angeles, the nation's second largest school district, identifies marked differences in the quality of individual teachers. That in and of itself should not be surprising, but the fact that a newspaper rather than school authorities conducted the analysis is disappointing.
"...Nevertheless, value-added analysis offers the closest thing available to an objective assessment of teachers. And it might help in resolving the greater mystery of what makes for effective teaching, and whether such skills can be taught.
On visits to the classrooms of more than 50 elementary school teachers in Los Angeles, Times reporters found that the most effective instructors differed widely in style and personality. Perhaps not surprisingly, they shared a tendency to be strict, maintain high standards and encourage critical thinking..."
But the surest sign of a teacher's effectiveness was the engagement of his or her students — something that often was obvious from the expressions on their faces."
"...Value-added analysis offers a rigorous approach. In essence, a student's past performance on tests is used to project his or her future results. The difference between the prediction and the student's actual performance after a year is the "value" that the teacher added or subtracted.
For example, if a third-grade student ranked in the 60th percentile among all district third-graders, he would be expected to rank similarly in fourth grade. If he fell to the 40th percentile, it would suggest that his teacher had not been very effective, at least for him. If he sprang into the 80th percentile, his teacher would appear to have been highly effective.
Any single student's performance in a given year could be due to other factors — a child's attention could suffer during a divorce, for example. But when the performance of dozens of a teacher's students is averaged — often over several years — the value-added score becomes more reliable, statisticians say.