The validity of teachers' reports of students' instructional experiences (content exposure or coverage) and content validity of a given course were studied by examining the consistency of reported content coverage for teachers across two consecutive years (1988 and 1989). In addition, the sensitivity of the test to instruction was examined by linking student performance patterns to instructional experiences of students as corroborating evidence of their relationship. Analyses were based on teacher and student data from approximately 300 sections of high school mathematics classes (approximately 2,000 examinees) in California using results from the Algebra Readiness and Elementary Algebra examinations of the Mathematics Diagnostic Testing Program. Twenty teachers responded to a questionnaire about their coverage of the mathematics topics in both years. Overall, results indicate that the prevalence and type of coverage of topics were consistent with their curricular sequence across years. Patterns were consistent with logical expectations for the topic within a given course across years and across teachers. Cross-validation of teachers' responses on content coverage in a specific topic category (for a specific course) was successful. Insight into instructional practices was provided by questionnaire responses. Three illustrative figures and three appendices providing content coverage figures in nine tables are provided. A 31-item list of references is included. (SLD)