School districts across the country are struggling with whether--and how--to incorporate multiple measures into teacher evaluation systems. In the District of Columbia, however, the decision has already been made. The D.C. IMPACT system, originally developed under former Chancellor Michelle Rhee, is a rigid, numerically based teacher evaluation system that rates teachers on the basis of classroom observations and student performance data. IMPACT replaces a previous teacher evaluation system that rated 95 percent of D.C. teachers "satisfactory" or above. Yet NAEP (National Assessment of Educational Progress) scores for District of Columbia students were among the lowest in the nation. In this report, the author takes readers inside the D.C. teacher evaluation process. She spent months talking with teachers. She sat in on classroom observations--and the subsequent conferences--by D.C. "master educators." She spoke with the District of Columbia administrators responsible for developing and implementing the program. She offers both an inside view of the process and some suggestions for how to make it stronger. (Contains 1 table, 2 figures and 19 notes.)