Moving teacher evaluation systems from measuring teachers' performance to improving their practice requires much greater attention to communication and support. In the fall of 2012, Chicago Public Schools (CPS) instituted a sweeping reform of its teacher evaluation system with the introduction of REACH Students (Recognizing Educators Advancing Chicago's Students), replacing a 1970's-era checklist rubric and for the first time including a detailed classroom observation process and student growth measures into teacher evaluations. Researchers at the University of Chicago Consortium on Chicago School Research have investigated teacher evaluation reforms in Chicago and several other districts in Illinois from 2008 to the present. This article draws on that research to present examples of the communication and support some districts have provided for rating teacher practice, as well as areas where communication and support are crucial for moving from solely measuring teacher practice to improving it.