• The coherence and integration of professional development programs.

As envisioned by the standards, teachers partake in development experiences appropriate to their status as professionals. Beginning with preservice experiences and continuing as an integral part of teachers' professional practice, teachers have opportunities to work with master educators and reflect on teaching practice. They learn how students with diverse interests, abilities, and experiences make sense of scientific ideas and what a teacher does to support and guide all students. They study and engage in research on science teaching and learning, regularly sharing with colleagues what they have learned. They become students of the discipline of teaching.

Reforming science education requires substantive changes in how science is taught, which requires equally substantive change in professional development practices at all levels. Prospective and practicing teachers need opportunities to become both sources of their own growth and supporters of the growth of others. They should be provided with opportunities to develop theoretical and practical understanding and ability, not just technical proficiencies. Professional development activities need to be clearly and appropriately connected to teachers' work in the context of the school. In this way, teachers gain the knowledge, understanding, and ability to implement the Standards.

The assessment standards provide criteria against which to judge the quality of assessment practices. They cover five areas:

• The consistency of assessments with the decisions they are designed to inform.

• The assessment of both achievement and opportunity to learn science.

• The match between the technical quality of the data collected and the consequences of the actions taken on the basis of those data.

• The fairness of assessment practices.

• The soundness of inferences made from assessments about student achievement and opportunity to learn.

In the vision described by the Standards, assessments are the primary feedback mechanism in the science education system. They provide students with feedback on how well they are meeting expectations, teachers with feedback on how well their students are learning, school districts with feedback on the effectiveness of their teachers and programs, and policy makers with feedback on how well policies are working. This feedback in turn stimulates changes in policy, guides the professional development of teachers, and encourages students to improve their understanding of science.

Ideas about assessments have undergone important changes in recent years. In the new view, assessment and learning are two sides of the same coin. Assessments provide an operational definition of standards, in that they define in measurable terms what