(Cohen and Hill, 1998; Elmore and Burney, 1998). This continued learning should include the development of cognitive models of learning. Teachers’ professional development can be made more effective if it is tied closely to the work of teaching (e.g., National Academy of Education, 1999). The “lesson study” in which Japanese teachers engage offers one way to forge this link (Stigler and Hiebert, 1999). In that approach, teachers develop lessons on their own, based on a common curriculum. They try these lessons out in their classrooms and share their findings with fellow teachers. They then modify the lessons and try them again, collecting data as they implement the lessons and again working collaboratively with other teachers to polish them. The resulting lessons are often published and become widely used by teachers throughout the country.
Recommendation 10: Policy makers are urged to recognize the limitations of current assessments, and to support the development of new systems of multiple assessments that would improve their ability to make decisions about education programs and the allocation of resources.
Important decisions about individuals should not be based on a single test score. Policy makers should instead invest in the development of assessment systems that use multiple measures of student performance, particularly when high stakes are attached to the results.
Assessments at the classroom and large-scale levels should grow out of a shared knowledge base about the nature of learning. Policy makers should support efforts to achieve such coherence.
Policy makers should promote the development of assessment systems that measure growth or progress of students and the education system over time and that support multilevel analyses of the influences responsible for such change.
Recommendation 11: The balance of mandates and resources should be shifted from an emphasis on external forms of assessment to an increased emphasis on classroom formative assessment designed to assist learning.
Another arena through which research can influence practice is education policy. This is a particularly powerful arena in the case of assessment. Policy makers currently are putting great stock in large-scale assessments and using them for a variety of purposes. There is a good deal of evidence