This study focuses on an issue of recent policy significance--the need to aid teachers in successfully identifying why children struggle to acquire literacy. This study (a) asked K-1 teachers to nominate students that they believed to be at risk for literacy difficulties and to provide reasons for their concern, (b) examined how these reasons relate to teachers' broader conceptions of literacy, and (c) investigated whether teachers' initial reasons and checklist-guided ratings align with concurrently administered standardized assessments. Results revealed that teachers have a wide array of initial concerns for students. There was some discordance between teachers' specific reasons for concern and their broader conceptions of early literacy. Comparison of student performance on standardized measures with teacher rationale also revealed discordance. Specific guidelines to teachers on use of a literacy checklist increased concordance between subsequent teacher ratings and standardized measures in some reading-related skills but not others. Implications for the use of multiple sources of evidence for student performance, as well as professional development, are discussed.