If it’s not valid, reliability doesn’t matter so much! More on VAM-ing & SGP-ing Teacher Dismissal
This post includes a few more preliminary musings regarding the use of value-added measures and student growth percentiles for teacher evaluation, specifically for making high-stakes decisions, and especially in those cases where new statutes and regulations mandate rigid use/heavy emphasis on these measures, as I discussed in the previous post.
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The recent release of New York City teacher value-added estimates to several media outlets stimulated much discussion about standard errors and statistical noise found in estimates of teacher effectiveness derived from the city’s value-added model. But lost in that discussion was any emphasis on whether the predicted value-added measures were valid estimates of teacher effects to begin with. That is, did they actually represent what they were intended to represent – the teacher’s influence on a true measure of student achievement, or learning growth while under that teacher’s tutelage. As framed in teacher evaluation legislation, that measure is typically characterized as “student achievement growth,” and it is assumed that one can measure the influence of the teacher on “student achievement growth” in a particular content domain.
A brief note on the semantics versus the statistics and measurement in
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The recent release of New York City teacher value-added estimates to several media outlets stimulated much discussion about standard errors and statistical noise found in estimates of teacher effectiveness derived from the city’s value-added model. But lost in that discussion was any emphasis on whether the predicted value-added measures were valid estimates of teacher effects to begin with. That is, did they actually represent what they were intended to represent – the teacher’s influence on a true measure of student achievement, or learning growth while under that teacher’s tutelage. As framed in teacher evaluation legislation, that measure is typically characterized as “student achievement growth,” and it is assumed that one can measure the influence of the teacher on “student achievement growth” in a particular content domain.
A brief note on the semantics versus the statistics and measurement in