There is a growing consensus that evidence of teachers' contributions to student learning should be a component of teacher evaluation systems, along with evidence about the quality of teachers' practice. Value-added models (VAMs), designed to evaluate student test score gains from one year to the next are often promoted as tools to accomplish this goal. However, current research suggests that VAM ratings are not sufficiently reliable or valid to support high-stakes, individual-level decisions about teachers. Other tools for teacher evaluation have shown greater success in measuring and improving teaching, especially those that examine teachers' practices in relation to professional standards. (Contains 2 tables and 2 figures.)