Teacher Education in Physics

of preparation. Although the topics that they are expected to
teach may appear simple to a physicist, it takes a significant
amount of time and effort to develop the depth of under-
standing needed to teach this material in a coherent manner,
rather than as a set of separate activities.

IV. RELATION BETWEEN TEACHER
PREPARATION AND STUDENT LEARNING

The assessment of the effectiveness of a physics program
for the preparation of teachers should focus on how well they
understand the content and process of physics. A major in-
centive for conducting such a program is to improve student
learning in K-12 classrooms. Therefore, it is also important
to assess the effect of the type of preparation that teachers
have received on the intellectual development of their stu-
dents. Making such judgments in a K-12 classroom is chal-
lenging, partly because access is difficult. Nevertheless, we
have been able to conduct some limited assessments.

To help teachers in our preservice course develop peda-

gogical content knowledge, we have them teach in a precol-

lege classroom a topic that they themselves have studied. In

the following example, preservice teachers designed and

taught lessons on the straight-line propagation of light to

ninth-grade students and then assessed the results.^19

A. Preparation of K-12 teachers

The preservice teachers began their study of this topic

with a pretest that has been given to more than 2000 students

from the introductory to the graduate level, and to many

K-12 teachers.^8 The part of the pretest in Fig. 5aasks what

would be seen on a screen when a mask with a triangular

hole is placed between a long-filament bulb and the screen.

As Table I indicates, preservice teachers and introductory

students performed at about the same level20%on the

pretest. About 65% of the graduate students responded cor-

rectly. In all three populations, many students could not ap-

ply the basic ideas that light travels in a straight line and that

every point on an object acts as a source of an infinite num-

ber of rays emitted in all directions.

After working through the relevant sections ofLight and

ColorinPbI, the preservice high school teachers developed

a ray model for light that they could apply to predict and

explain the patterns formed on a screen by light sources and

apertures of various shapes.^20 Two of the many post-tests

that we have administered are in Fig. 5b. As Table I shows,

the preservice teachers did better afterPbIinstruction85%

than physics graduate students did on the simpler pretest.

B. Effect on K-12 students

After they had acquired the background discussed in Sec.

IV A, the preservice teachers modified the relevant sections

ofPbIand used these sections in a ninth-grade classroom.

They then assessed the performance of their students with

one of the post-tests in Fig. 5b. About 45% of the ninth-

grade students gave a correct responsesee Table I. If these

students had learned from teachers with only a typical back-

ground, they would have likely done no better than their

teachers or university undergraduates20%. Table I also

contains results85%from other ninth-grade students taught

by an experienced teacher who was thoroughly familiar with

both the content and instructional approach inPbI. Not sur-

Fig. 5.aPretest andbpost-test questions on light and apertures. Students
are asked to predict what they would see on a screen when assorted aper-
tures are placed between various extended light source and the screen.

Table I. Percentage of correct responses on pretest and post-test questions on light and apertures. Pretest results

are from a question about a long-filament bulb and a triangular aperturesee Fig. 5a. Post-test results are from

questions about various light sources and aperturessee Fig. 5b. The preservice teachers had worked through

the relevant sections ofPbIbefore modifying the curriculum. The experienced inservice teacher was thoroughly

familiar with the content and with thePbIapproach.

Pretest Post-test

Undergraduates

and preservice

teachers9-12

Graduate

TAs

Preservice

teachers

9-12

Ninth-grade students

after standard

instruction

after standard

instruction

afterPbI after PbI

modified by

well-prepared

preservice teachers

after PbI

modified by

very well-prepared

inservice teacher

N 2000 N 110 N 60 N 55 N 55

20% 65% 85% 45% 85%

766 Am. J. Phys., Vol. 74, No. 9, September 2006 McDermottet al. 766