duced instructional programs with demonstrated student achievement benefits. In physics, for example, a highly productive tradition of research has produced a deep knowledge base with very important implications for educational practice. In contrast, for other areas in science education the research base is not yet developed fully enough to guide or support decisions about instruction. As with reading comprehension, knowledge of the progression of student understanding is relatively sparse and spotty from topic to topic. Moreover, there is very little evidence about how student understanding can develop with instruction over the school years.
The first section of this chapter, as in the chapters on mathematics and reading, addresses an area that has potential for wide impact in the relatively near term: physics. Unlike the other two disciplines, however, this downstream case falls late in the K-12 curriculum. The second section of this chapter addresses science education across the school years, since we are still far upstream in developing a principled organization of science instruction, particularly in the years before high school.
The number of students who take courses in physics is relatively small in comparison to the number who take biology or chemistry, as is the number of credentialed high school physics teachers in comparison to other science teachers. Perhaps because the community of educators working on physics is small, it has been possible to pursue a cumulative research agenda on major issues in physics teaching and learning.
Until relatively recently there was substantial overall agreement regarding what students should know and be able to do in the typical high school or college physics course (the content of the two overlaps substantially). In general, students were ex