Criteria for judging performance are traditionally and unproblematically invoked as a resource to be used (1) to make the assessment requirements evident to learners and (2) to provide a tool for rendering teacher judgments consistent, reliable, and fair. This paper explores the use of criteria and standards in the process of teacher judgment of student performance. The analysis suggests that, beyond criteria, judgments are constructed by and construct teachers' professional identities. It also suggests that attending systematically to teachers' professional knowledge contributes to an understanding of how teachers construe performance, and the "construct" upon which assessments are based. (Contains 1 table.)