tween 1.7 million and 2.7 million new teaching positions (National Center for Education Statistics (NCES), 1999a).
Of those new teaching positions, about 200,000 will be in secondary science and mathematics (NRC, 2000a). In the face of the current shortages of qualified teachers, there is no reason to expect that a significant percentage of the people hired for these positions will be proficient in both subject-matter background knowledge and pedagogy in these subject areas. Among high school physics teachers, for example, 32 percent have a degree in physics or physics education and have taught it on a regular basis, 41 percent have no physics degree, but have extensive physics teaching experience, and 27 percent have no physics degree and little physics teaching experience (American Institute of Physics, 1999). Another report (Ingersoll, 1999) indicates that approximately 33 percent of mathematics teachers and 20 percent of science teachers in grades 7-12 do not have either a major or minor in their field. These underqualified teachers teach more than 26 percent of mathematics students and more than 16 percent of science students. In urban and small rural school systems, especially those with large populations of students in poverty, the percentages of underqualified teachers are even higher.
Having well-prepared teachers is central for students’ becoming literate in science, mathematics, and technology. A report by the NCTAF (1996) unequivocally shows the positive effect of better teaching on student learning. Another study, by the Center for the Study of Teaching (Darling-Hammond, 1999), found that the two most consistent and powerful predictors of student achievement in science and mathematics were having teachers who were both fully certified and had a college major in the subject being taught. These findings about the importance of qualified teachers are consistent with research on what experts know and how they can use that knowledge. Teachers with content expertise, like experts in all fields, understand the structure of their disciplines; they thus have cognitive “roadmaps” to guide the assignments they give students, the assessments they use to gauge student progress, and the questions they ask in the give and take of the classroom (NRC, 1999b).
Teachers face a further challenge in the classrooms of the twenty-first century: the increasing diversity of the nation’s schoolchildren. The waves of immigration to the United States in the last decades of the twentieth century have filled the schools with children from myriad cultural and ethnic backgrounds; these students have varying degrees of English proficiency when they begin school. Fairfax County, Virginia, a suburb of Washing-