Value-added Modeling

Value-added modeling is a method of teacher evaluation that measures a teacher's contribution in a given year by comparing their students' current test scores against those same students' scores in previous years and against the scores of other students in the same grade, seeking to isolate the value a given teacher adds independent of the students' starting point. It is considered fairer than simply comparing raw achievement or gain scores without accounting for confounding factors such as past performance or income, and the same approach can be extended to estimate the value added by a principal or a school as a whole. Critics argue that using test scores this way to evaluate individual teachers has not been scientifically validated and that results are often shaped by chance or by conditions outside a teacher's control, though research has found that measured differences in teacher effectiveness are associated with small economic effects on students.