Highlights
- Value-added measures are positively related to almost all other commonly accepted measures of teacher performance such as principal evaluations and classroom observations.
- While policymakers should consider the validity and reliability of all their measures, we know more about value-added than others.
- The correlations appear fairly weak, but this is due primarily to lack of reliability in essentially all measures.
- The measures should yield different performance results because they are trying to measure different aspects of teaching, but they differ also because all have problems with validity and reliability.
- Using multiple measures can increase reliability; validity is also improved so long as the additional measures capture aspects of teaching we value.
- Once we have two or three performance measures, the costs of more measures for accountability may not be justified. But additional formative assessments of teachers may still be worthwhile to help these teachers improve.
Introduction
In the recent drive to revamp teacher evaluation and accountability, measures of a teacher’s value added have played the starring role. But the star of the show is not always the best actor, nor can the star succeed without a strong supporting cast. In assessing teacher performance, observations of classroom practice, portfolios of teachers’ work, student learning objectives, and surveys of students are all possible additions to the mix.
All these measures vary in what aspect of teacher performance they measure. While teaching is broadly intended to help students live fulfilling lives, we must be more specific about the elements of performance that contribute to that goal – differentiating contributions to academic skills, for instance, from those that develop social skills. Once we have established what aspect of teaching we intend to capture, the measures differ in how valid and reliable they are in capturing that aspect.
Although there are big holes in what we know about how evaluation measures stack up on these two criteria, we can draw some important conclusions from the evidence collected so far. In this brief, we will show how existing research can help district and state leaders who are thinking about using multiple measures of teacher performance to guide them in hiring, development, and retention.
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