This project evaluated the relationship between assessment practices and achievement and the mediating roles of student self-efficacy and effort. In part, this was based on a framework proposed by Brookhart (1997). The United States portion of the Third International Math and Science Study was used to estimate these relationships. Several student level characteristics were important explanatory variables regarding variation in mathematics achievement, including mathematics self-efficacy, effort, and level of uncontrollable attributions. At the classroom level, teacher assessment practices had significant relationships to classroom performance. In addition, cross-level interactions (between student characteristics and teacher practices) suggested that classroom assessment practices might uniquely interact with student characteristics in their role of motivating student effort and performance.