Study backs 'value-added' analysis of teacher effectiveness

The L.A. Times reports:

Teachers' effectiveness can be reliably estimated by gauging their students' progress on standardized tests, according to the preliminary findings of a large-scale study released Friday by leading education researchers.

The study, funded by the the Bill and Melinda Gates Foundation, provides some of the strongest evidence to date of the validity of "value-added" analysis, whose accuracy has been hotly contested by teachers unions and some education experts who question the use of test scores to evaluate teachers.