Teachers want to succeed, but the conditions for success aren’t always in place, leaving educators on their own to adjust practice. This summary offers a set of guiding principles to inform the design and implementation of high-quality teacher support and evaluation systems based on three years of work by the Measures of Effective Teaching (MET) project, its partners, and other leading school systems and organizations. More in-depth discussion of the MET project’s analyses to date may be found in the project’s research reports and non-technical briefs here.