Lillian C. McDermott
25
History
3/15/10
Post-tests on the geometric image produced by a light source and aperture.
To determine the effect of our physics courses for teachers on learning by K-12
students, we have examined data from a short practicum that is part of our preservice
program.
(Former Institute participants are another source of information.
They often
share results with us from pretests and post-tests that they have given their students.)
After acquiring a thorough understanding of the ray model, the preservice teachers
draw on their experience with
PbI
to design lessons that they teach in a ninth-grade
classroom.
They also assess the progress of their 9
th
grade students.
Post-test results from
the ninth-graders (45%) have been significantly better than the pretest performance of the
K-12 preservice and inservice teachers (20%) before they have worked through
PbI
.
The
ninth-grade results show the positive impact that well-prepared teachers can have on
student learning. Inexperienced teachers who have a thorough understanding of the
concepts and are also familiar with research-based instructional materials are better able to
help students learn than those who are experienced but lack a sound understanding of the
content.
Inservice teachers, who are both well prepared and experienced, do even better.
The practicum helps convince prospective teachers of the importance of an in-
depth understanding of the content. Most Summer Institute participants quickly perceive
the difference between teaching what they have memorized and what they understand.
Although most have already “known” that “light travels in a straight line,” few have been
able (without targeted instruction) to apply this knowledge.
We have found that
experience in teaching a topic is not a reliable indicator of conceptual understanding.
Other Topics
There are many other topics in science that K-12 teachers are expected to teach.
Following are three for which our research has shown the need for targeted help.
Balancing
61
is a unit in many elementary school curricula.
We probed understanding of
this concept in two different populations: about 700 students in introductory calculus-
based physics and about 50 inservice K-5 teachers.
Many of these teachers had previously
taught units on balancing.
Students were shown a sketch of a baseball bat balanced on a
61
L.G. Ortiz, P.R.L. Heron, and P.S. Shaffer, “Student understanding of static equilibrium: Predicting
and accounting for balancing,”
Am. J. Phys.
73
(6), 545 (2005).
Lillian C. McDermott
26
History
3/15/10
finger and were asked to compare the total mass to the left and right of the balance point.
Only about 20% of the introductory students and 15% of the K-12 teachers responded
correctly. Almost all incorrect answers claimed there must be equal mass on both sides.
The treatment of balancing in
PbI
has been effective in
addressing this mistaken belief.
Sinking and Floating
62
is a popular topic in elementary school science.
It is introduced in
Properties of Matter
through careful development of the concepts of mass, volume, and
density.
Archimedes Principle is taught in introductory physics in the context of buoyant
force.
These students have not done as well as our elementary school teachers in
predicting whether five blocks of the same size but different mass will sink or float.
Control of Variables
63
is a reasoning skill that K-8 students are expected to acquire.
Their
teachers must be able to decide whether a variable determines, influences, or has no effect
on the outcome of a given experiment or other situation.
In collaboration with Andrew
Boudreaux (Western Washington U.), who had earned his Ph.D. with our group, we
examined control of variables in a general education physics course at WWU and in the
calculus-based course at UW. K-8 teachers from our Summer Institutes and short
workshops were included.
All had similar serious reasoning difficulties.
Helping students
develop this reasoning skill remains a challenge.
F.
Publication of
Physics
by Inquiry
A preliminary version of
Physics by Inquiry
was used at UW and at a few other
institutions during the 1980s and early 1990s.
Despite its apparent success, we delayed
formal publication. Finally, Cliff Mills (then Physics Editor at Wiley) persuaded Peter
and me that the time had come.
We agreed to a publication date in 1996, reluctantly
admitting that perfection is not possible.
By this time,
PbI
contained initial or revised
versions of:
Properties of Matter, Kinematics
,
Electric Circuits
,
Heat and Temperature
,
Astronomy by Sight
,
Light and Color
,
Light and Optics
,
Magnets
, and
Electromagnets.
64
62
M.E. Loverude, C.H. Kautz, and P.R.L. Heron, “Helping students develop an understanding of
Archimedes’ principle I. Research on student understanding,”
Am. J. Phys.
71
(11), 1178 (2003) and
P.R.L. Heron, M.E. Loverude, P.S. Shaffer, and L.C. McDermott;
ibid.
“II.
Development of research-
based instructional materials,”
ibid
.
71
(11), 1188 (2003).
63
A. Boudreaux, P.S. Shaffer, P.R.L. Heron, and L.C. McDermott,
“Student understanding of control of
variables:
Deciding whether or not a variable influences the behavior of a system,”
Am. J. Phys.
76
(2),
163 (2008).
64
See III.c. in the Endnotes.
