Many factors should be considered in formally evaluating a teacher; however, nothing is more important than effectiveness in the classroom. Value-added models are an important tool for measuring student achievement and school effectiveness. These models have the ability to measure individual students' learning gains, controlling for students' previous knowledge and background characteristics. While some research suggests value-added models are subject to bias and statistical limitations, rich data and strong controls can eliminate error and bias. In the area of teacher quality, examining student growth offers a fairer and potentially more meaningful way to evaluate a teacher's effectiveness than other methods schools use.
Unfortunately, districts have used many evaluation instruments, including some mandated by states, which are structured so that teachers can earn a satisfactory rating without any evidence that they are sufficiently advancing student learning in the classroom. Teacher evaluation instruments should include factors that combine both human judgment and objective measures of student learning.
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