We examine the efficiency implications of imposing proportionality in teacher evaluation systems. Proportional evaluations force comparisons to be between equally-circumstanced teachers. We contrast proportional evaluations with global evaluations, which compare teachers to each other regardless of teaching circumstance. We consider a policy where administrators use the ratings from the evaluation system to help shape the teaching workforce, and define efficiency in terms of student achievement. Our analysis indicates that proportionality can be imposed in teacher evaluation systems without efficiency costs under a wide range of evaluation and estimation conditions. Proportionality is efficiency-enhancing in some cases. These findings are notable given that proportional teacher evaluations offer a number of other policy benefits.