There is growing interest among researchers, policy makers, and practitioners in identifying teachers who are skilled at improving student outcomes beyond test scores. However, questions remain about the validity of these teacher effect estimates. Leveraging the random assignment of teachers to classes, I find that teachers have causal effects on their students' self-reported behavior in class, self-efficacy in math, and happiness in class that are similar in magnitude to effects on math test scores. Weak correlations between teacher effects on different student outcomes indicate that these measures capture unique skills that teachers bring to the classroom. Teacher effects calculated in nonexperimental data are related to these same outcomes following random assignment, revealing that they contain important information content on teachers. However, for some nonexperimental teacher effect estimates, large and potentially important degrees of bias remain. These results suggest that researchers and policy makers should proceed with caution when using these measures. They likely are more appropriate for low-stakes decisions--such as matching teachers to professional development--than for high-stakes personnel decisions and accountability.