Who teaches the DCIs?
To teach high school physics in any state, you have to be licensed in that state. Different states have different requirements. In Illinois, with which I am most familiar, to teach physics in high school, you need to have a BS in one of the sciences: physics, chemistry, biology, and earth and space science. In most universities, including mine – the state’s oldest public university and recognized for its teacher preparation programs – to get a BS in chemistry, biology, or earth and space science, you need at most two physics courses. To grasp the level of the physics courses in which various majors enroll, I’ll look at the range of introductory courses offered by a typical physics department.
- The general education course conveying the “excitement” of physics; no prerequisite; very little math – nothing beyond arithmetic and power-of-ten notation. This is the course designed to be taken by any student on campus.
- The concepts-in-physics course, which uses very little algebra and is required by some departments who think that the level of the previous course is too low. This course covers mostly mechanics and electromagnetism, waves, some thermodynamics, and very little atomic and nuclear physics. Its level is below what a high school physics course should be.
- The algebra-based courses taught in two semesters. The first course covers mechanics, heat, and waves; the second course covers electromagnetism, quantum, atomic, and nuclear physics. These are the courses taught in two years at high schools with good physics teachers.
- The calculus-based courses are a sequence of three to four courses covering mechanics, electromagnetism, waves, thermodynamics, and quantum and atomic physics. All of them are taken by all physics majors. Good chemistry programs require their majors to take the first two, covering mostly mechanics and electromagnetism as well as waves or thermodynamics.
To obtain a BS in biology, you have to take only one physics course. The vast majority of the biology majors who intend to be high school teachers take the second course above. The mathematics requirement of this degree is just algebra plus some probability.
Therefore, the physics background of a typical graduate of the biology teaching program is below a good high school physics course!
To obtain a BS in earth and space science education, you have to take only two physics courses, one of which usually covers astronomy at the level of a general education course (first course above), and the other one is the first of the algebra-based sequence. There is no explicit mathematics requirement for this degree, and the implicit requirement for the more advanced physics course is two years of high school algebra. To obtain a BS degree in chemistry education, you need two semesters of the calculus-based physics and two semester of calculus.
Now consider the following disturbing statistics:
Almost two thirds of American high school physics teachers don’t have a degree in physics!
Assuming that they have a degree in one of the other three sciences – which is not necessarily the case, as some rural schools allegedly confuse physical “education” with physical science and have their football coach teach physics – and that these degrees are equally divided in that population, we obtain the bleak situation of more than 20% of the teachers having passed (most likely with a grade of C) a single course at sub-high school level, over 20% having had a high school course that covers only mechanics, and another 20% having had only two introductory university physics courses covering mostly mechanics and electromagnetism.
What about the other third who do have a BS in physics teaching? I have had direct, long-term, and evaluative experience with this group at their sophomore/junior year. Barring a few exceptions in the last twenty years or so, generally the students in our teaching program were in the lowest quarter of the class. Since my course was about applying mathematical techniques to physical problems, I could evaluate these students’ mathematical as well as physical ability. Although they had had at least two semesters of calculus and two semesters of calculus-based physics, their understanding of both subjects was poor. They often mixed the concepts of velocity and acceleration, they had trouble calculating components of electric and magnetic fields, and they could not set up the integral of the electrostatic potential of a simple charge distribution. Their mathematical skill was abysmal. I routinely saw “identities” like (but the rule changes if ; it becomes ) and ! The only trigonometric identity that all of them knew was the fact that the sum of the squares of sine and cosine was 1. However, if the two squares appeared in an algebraic expression but were both multiplied by the same constant and separated by some other terms, many of them did not have the sense of factoring out the constant and setting the sum equal to one!