• Professional development should provide opportunities to gain an understanding of the theory underlying the knowledge and skills being learned.
• Professional development should be connected to a comprehensive change process focusing on improving student learning.

Other research suggests that the content of professional development is related to its effectiveness. The most effective subject of professional development appears to be focused on the content teachers teach. In one major study of teachers in California, teachers who participated in learning opportunities focused on the curriculum—lessons they were teaching—were more likely to change their practice than those who participated in sessions dealing with special topics, like cooperative learning or diversity, that are more abstract and less directly related to the content the teachers teach (Cohen and Hill, 1998). Moreover, the curriculum-based professional development also appeared to affect student learning: students whose teachers participated in curriculum sessions outperformed others on the state test. Significantly, however, the study found, teachers' opportunities for professional development varied. Teachers of more affluent students were more likely than teachers of disadvantaged students to take part in the curriculum workshops, and teachers of disadvantaged students participated in the special topics workshops more often.

Other areas of professional development that appear to have an impact on changing practice are activities centered on student assessment. In Kentucky and Vermont, portfolios in mathematics and writing have had a strong influence on instruction (Stecher et al., 1998; Koretz, et al., 1996). Teachers say that training in scoring portfolios has helped them understand the characteristics of high-quality work and the teaching strategies that help to produce such work. Teachers also report that scoring performance assessments has had the same effect.

However, researchers have found that teachers have had few opportunities to learn about classroom assessment—the frequent assessments they undertake to monitor their students' progress over the course of the year. Teacher preparation programs provide little emphasis on measurement (Plake and Impara, 1997), and most instruction in measurement focuses on technical assessment issues, rather than strategies for gauging student progress (Calfee and Masuda, 1997). Largely as a result, teachers say they feel inadequately prepared in assessment (Aschbacher, 1994).

• Districts should design professional development that is focused on the standards for student performance.
• Districts should use results from student assessments and