NCPA - National Center for Policy Analysis

The Value Added By a Teacher Can Be Measured, Say Experts

December 29, 1999

There is a spreading movement to improve public education by making schools more accountable for student performance, basing such things as extra funding on student test scores and graduation or drop-out rates. Students are also being held accountable for learning, through efforts to end social promotions of failing students. And there is also a growing consensus that some form of teacher evaluation is necessary.

Theoretically, the system should reward good teachers through merit pay and/or advancement -- and provide a basis for weeding out bad teachers. The problem is how to design a system that is effective, but doesn't alienate good teachers.

  • Weeding out bad teachers is a task performed by effective principals -- in school districts without union collective bargaining.
  • However, the evaluation of teachers, such as the peer reviews favored by teachers' unions, has always been subjective.
  • But many researchers say the availability of the right kind of data could allow them to objectively determine teachers' effectiveness.

Leading this research is William L. Sanders, a statistician at the University of Tennessee, who has developed a complex statistical model that measures the "value" a teacher adds to his or her students based on the change in their test scores over a given year. It factors out such variables as socioeconomic status or low-achieving students, so that it doesn't matter where the students start, only what they achieve during the year.

In Tennessee, the state's assessment system allows Sanders' "value-added" numbers to be incorporated into formal teacher evaluations.

And Denver schools have set up the first plan in the country to tie teachers' bonuses to their own students' achievement. The two-year pilot program offers teachers an annual bonus of up to $1,500 if their students meet specified goals.

Source: Siobhan Gorman, "How Should Teachers Be Evaluated?" National Journal, December 4, 1999.


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