So little time ... so much to cover! Thus runs the physics teacher's lament. I see my students for three or at most four hours weekly; they spend, at best, as much time again on homework - and together we are expected to make meaningful contact with the whole of classical physics: kinematics; Newton's Laws; gravitation; static electricity; circuits; magnetism; light, waves, sound, and optics ... a body of knowledge that dozens (if not hundreds) of great thinkers spent entire lives creating.
If you have to prepare your students (or yourself) for comprehensive exams - Advanced Placement; the subject SAT; or a state-mandated test such as Massachusetts' MCAS - then, alas, you have little choice in the matter: you've got to cover the curriculum, A to Z.
I'm somewhat lucky: for a variety of reasons I personally don't have to prepare (most of) my students for such exams. However, I still am obliged to touch base with my state's curriculum frameworks for introductory physics. And so the dilemma remains: breadth (touching briefly on every major topic) or depth (selecting a few for full immersion)?
My dilemma has been sharpened by two recent readings. One: Five Easy Lessons, a book about physics teaching by Randall Knight, one of my favorite textbook authors. Knight points out that even his college students often are unfamiliar with the basic phenomena that physics aims to explain: the varied interactions among magnets; the images formed by mirrors and lenses; the practical consequences of voltage and current; and so on. If his students at an admired California university are so unfamiliar with these phenomena, then high-school students presumably are similarly bereft.
The other was published online last December in the journal Science Education. In it, Marc Schwartz (University of Texas, Arlington) and three colleagues looked at the grades that students got in first-year college courses in biology, chemistry, and physics. Next, they set up a system for the students to classify their high-school courses in those subjects as broad or narrow, shallow or deep. Finally, they correlated students' descriptions of their high-school science courses with their first-year college performance.
The result? A deep high-school science course - one that spends at least a full month on a single topic, such as magnetism or covalent bonds - always makes it likelier that a student will do well in his or her college-level course on the same subject. Broad but shallow courses, for their part, are correlated with poorer performance. The effects were most striking in biology and weakest (but still significant) in physics.
Why should you care? Well, if you (or one of your children) is taking science in a public school, you probably know that students and teachers alike are pushed toward breadth (hitting as many topics as possible) and away from depth (spending lots of time on one) by standardized tests and comprehensive curriculum frameworks, which ambitiously try to encompass myriad topics within each of the major scientific fields.
And so we come full circle, to Knight's contention: namely, that there is no point in teaching the formulas and concepts behind phenomena if students haven't made first-person contact with those phenomena. I'm a relatively new teacher, but I can tell you that standing in front of a room full of teenagers and saying, "you know, if you hold two magnets together ... " only draws blank stares or discipline-testing disengagement. For some students do know, and others do not; and even those who do may not have systematically noted the various permutations of N and S poles that are so central to my lecture.
So out come the magnets. Students smile; hands reach outward; eyes and fingertips send stimulating signals to both cerebral hemispheres; misconceptions fall victim to evidence ... and a precious hour of class time is consumed. There's no better way to spend that time, granted; but I have used up fully one-fourth of the time that I can devote to basic magnetism - that is, if I am to hit all of the topics on my state's curriculum frameworks for introductory physics. (The dilemma is sharper yet for my colleagues who teach chemistry and biology - subjects where labs require much more prep time and where phenomena take hours, weeks, even months to unfold.)
I hope that the well-meaning (and I mean it sincerely) policy wonks, school-board members, and politicians will come to Room A302 (or its equivalent) and spend an hour wrestling with real and virtual images; series and parallel circuits; free fall and terminal velocity. Then I hope they will reexamine their ambitious goals for introductory high-school science classes and then (as the saying goes) "do the math."
Copyright 2009 Joshua Roth. All rights reserved.