[1]Exploring the Place of Exemplary Science Teaching, (Haley-Oliphant, 1994), includes several chapters that discuss teaching as inquiry into student understanding and participation. See especially the chapters "Improvisational teaching" by Julia Riley, "Improvising learning conversations" by Robert Yinger and Martha Hendricks-Lee, "How do I read my students?" by Betty Wright, and "Learning from the stories of science teachers" by Kenneth Tobin. Other writings include Duschl and Gitomer (1997), in which they describe "assessment conversations" as tools for teacher inquiry into student understanding, and Hammer (1997), in which I present an account of my inquiry as the teacher in a high school physics class.
 

[2]See Schsn (1983) for an account of the nature of expertise in "reflective practitioners."
 

[3]All of the schools listed are Massachusetts public secondary schools, with the exception of Dana Hall, which is a private school for girls. I recruited teachers for this project through mailings and phone calls to local high schools, and the teachers were compensated as consultants. The project began in March 1995 under the auspices of the Teachers' Resources Network of the Center for the Development of Teaching, at the Education Development Center in Newton MA, from a grant by the Dewitt Wallace-Reader's Digest Fund. That funding ended in June, 1996, but we were awarded a grant to continue for two years, beginning in August, 1996, by the MacArthur /Spencer Professional Development Research and Documentation Program.
 

[4]All of the schools have recognizable distinctions between levels of physics classes. At the top level are the Advanced Placement classes, which are almost always the second year of physics instruction. Among the first year courses, there are the "honors" courses, which may be calculus-based; algebra-based "college-prep," courses, typically with two or three sections; and, at some schools, a "conceptual" level with minimal mathematics.
 

[5]The discussion here concerns the skydiver's fall before he opens his parachute. Readers who are not familiar with Newtonian mechanics may wish to consult the appendix for a brief explanation.
 

[6]Ellipses (. . .) indicate where I have omitted portions of the transcript. Square brackets ([like these]) indicate words I have substituted or added to the transcript for clarity.
 

[7]Ohm's Law is a relationship among the electric potential, or voltage, (V), the current (I), and a resistance (R), usually written "V = IR." It states, in essence, that the voltage across a resistor and the current through the resistor are proportional: The higher the resistance, the greater the ratio of voltage to current.
 

[8]Gentner and Gentner (1983) discussed students' different mental models of electric current and voltage.
 

[9]Brown, Collins, and Duguid (1989) is probably the most well-known reference.
 

[10]It is for this reason that I have mostly referred to teachers' interpretations as "perceptions" and researchers' as "perspectives." It is not to imply that teachers do not have perspectives or that researchers are unperceptive; it is to connote different modes of inquiry, one more characteristic of teaching and one more characteristic of research. The practice of research requires that interpretations be made articulate, in presentations, publications, and proposals, whereas the practice of teaching requires action, responding to students during class, choosing or designing materials and assignments. To act responsibly, teachers must perceive more than anyone could articulate; to be articulate, researchers must omit from their perspectives much of what they see.
 

[11]For extended discussions of the value of teacher inquiry for education research, see Cochran-Smith and Lytle (1993) and Schifter (submitted).