A study explored the nature and quality of teacher-developed assessment instruments. Teachers (n=228) from a range of grades, subjects, and school districts described patterns of test use, concerns about assessment, and use of performance assessment by completing an extensive questionnaire. The research was conducted to determine: (1) teachers' skills, attitudes, perceptions, and concerns about day-to-day classroom assessment; (2) the extent to which performance tests (versus other forms of assessment) are used in classrooms; (3) the nature of performance tests; and (4) whether (or how) teachers check and/or attempt to improve the quality of their classroom performance assessments. Results suggested that the foundation and structure of classroom assessment consists primarily of teacher-developed assessments, with performance assessment serving as one of the key tools. Five major issues are analyzed and discussed: (1) the use and importance of performance assessment in the classroom; (2) the stability of results across grades, subjects, and research contexts; (3) teachers' concerns about assessment, particularly with respect to improving test quality and use; (4) specific issues of assessment quality, including potential difficulties in classroom performance assessment procedures; and (5) actions needed to overcome some of the assessment problems. (Author/JD)