The current study explores how principals (n = 568) experience a new teacher evaluation model under Race to the Top. Findings suggest that principals felt the least confident in their ability to identify teacher behaviors associated with student achievement gains and placed the least value on student achievement data. Evaluation experience predicted principals' knowledge and ability, which, in turn predicted valuation of data sources. Principals' valuation of data sources varied by accountability and locale. Findings help policymakers, principal educators, and professional development providers understand the role of individual and school contexts in how principals approach new teacher evaluation models.