Achieving a fair and objective evaluation of teacher performance is not easy. Student test results have been used to assess teacher performance, but this approach has many weaknesses, especially because students differ from school to school and standardized tests are open to questions about their fairness. Criterion-referenced tests have been developed to counteract some weaknesses apparent in norm-referenced standardized tests, but even these tests have weaknesses. For one thing, student performance is measured on only one occasion. Other criticisms may be leveled for the out-of-context nature of criterion-referenced tests. Portfolio use, however, stresses a philosophy of contextualism in appraising teacher effectiveness. Assessment through portfolios is not isolated and does not stress a numerical result unless rubrics are used. Even then, rubric ratings are open to human interpretation. Portfolios and their contents need to be aligned with stated objectives to be fair assessments, but their use can help gauge student learning and teacher effectiveness. (SLD)