Thursday, August 10, 2006

The Highly Qualfied Physical Science Teacher

What content knowledge is needed to be an effective science teacher? I began pondering this question when, by a quirk in NJ standards, I was required to take content knowledge tests in both physics and chemistry. Until 2004, NJ did not have separate chemistry and physics certifications. They only had physical science certification. This required knowledge of both chemistry and physics.

If one had trained to be such a combined physics/chemistry teacher then there would be no problem. However, NJ gets a substantial fraction of these science teachers through its alternate route programs. Typically such an alternate route candidate would have a background in chemistry or physics, but not both. Such was my case.

I know physics but not chemistry. I have advanced degrees in physics. My chemistry background consists of high school chemistry and one course in physical chemistry as a college freshman. That was more than 30 years ago. I have not had much contact with chemistry since. I have had no organic chem and no biochem — both of which are on the Praxis II test that NJ uses. In my opinion, I do not have the content knowledge necessary to teach high school chemistry (nor would I meet the current NJ requirement of at least 15 college credits).

If you have been following my earlier posts, you can guess how NJ got the physics people to pass chemistry and the chemistry people to pass physics. It just set very low standards. To earn physical science certification NJ required three tests. For physics, they used the one-hour Praxis II (10261) test of physics content knowledge, for chemistry the one-hour Praxis II (20241) test of chemistry content knowledge. [They also required a Praxis II test in General Science (10431) that includes biology.] The pre-2004 NJ cut-scores were a 119 for chemistry (19% of the scaled points possible) and a 113 for physics (13% of the scaled points possible).

How low these scores are, was put into perspective for me by my performance. I surpassed the chemistry cutoff by more than 60 points. This was my moment of enlightenment. Something was seriously wrong if my level of chemistry knowledge was more than 4 times the “highly qualified” minimum.

A majority of states use the two-hour versions of the Praxis II content knowledge tests (10265 and 20245). In chemistry, the cut-scores run from a high of 158 (Delaware) to a low of 135 (South Dakota). The 85th percentile score is 184. Assuming the one- and two-hour tests are comparable, it is comforting to know that at least 15% of the chemistry teachers know more chemistry than me. Cut-scores for individual states can be found on the ETS website (here) or at each state’s Department of Education website.

In physics the high cut-score is 149 (Indiana), the low 126 (West Virginia). The 85th percentile score is a 177. Delaware sets a cut-score of 112 on the one-hour physics test, a truly abysmal standard. Utah requires these tests but sets no cut-score. My guess is that Utah will eventually set cut-scores at that level that gives them an adequate supply of teachers. Objective standards, objective standards, we don’t need no stinkin’ objective standards.

Further analysis of these results is problematic. The Education Trust did not review the content of these exams, so what follows is entirely my own opinion. On the previously discussed math Praxis II, I thought a high score (above 180) was solid evidence of mastery. The physical science tests simply do not have content challenging enough for me to reach a similar conclusion. To score highly on the physics test, one only needed rote knowledge of a few formulas. Few of the questions tested concepts. One could have a high score and still have a poor conceptual understanding of the subject. Similarly, in chemistry I would not claim mastery of either rote knowledge or concepts and yet I had a high score.

Prior to NCLB and its “highly qualified” provisions, the minimal ability definition was a do no harm standard:
In all professional licensure assessments, minimum competency is referred to as the point where a candidate will “do no harm” in practicing the profession.
The post-NCLB era uses loftier language,“highly qualified”, but hasn’t actually raised the standards. In my opinion, on these tests, scores below 160 fail the “no harm” standard. Essentially these teachers have failed (scored below 60%) on a test of fairly rudimentary rote subject knowledge. I suspect these low scoring prospective teachers would also struggle on the SAT II or AP tests, yet we are saying they are “highly qualified” to help prepare our children to take these exams.

You should not have to take my word for it. It would be nice if old versions of these tests passed into the public domain. Without this level of transparency, the level of these tests remains largely hidden from public scrutiny. You can get some idea from the sample tests I linked to, but to really understand you need to see all the questions on a real test.

Before closing this topic, an appeal to anyone who can clarify the situation in Delaware. Delaware sets the lowest standard in physics, a 112 (on the one-hour test). They set the highest standard in chemistry, a 158 (on the two-hour test). They are transitioning their chemistry test from the one-hour to the two-hour. On the one-hour test their cut-score was a very low 127. Is the two-hour test much easier than the one-hour test? If not, I do not understand these vastly different standards. Is Dupont laying off chemists, thereby providing a surplus of potential teachers? Please leave a comment if you know something.


Jenny D. said...

Wow. What's funny is that none of this asks whether people can teach. Surely there are better ways to transmit content knowledge than others, but is this part of the test for teacher, this idea about better pedagogy?

Dr. P. said...


You'll get no argument from me that pedagogy is important too, but I have yet to see a accurate test of teaching ability. Content knowledge can be objectively assessed, especially in math and science (it's a separate debate whether the Praxis II tests do this), so shouldn't we measure it? And shouldn't we be concerned when many prospective teachers test so poorly.

Brad Hoge said...

It is indeed appalling to think about the low content standards actually achieved through NCLB, but your post brings up another dangerous aspect, that of confusing content mastery with subject literacy. I use the term literacy here to mean the ability to translate knowledge into problem solving, particularly problems without present solutions. When we teach math and science, isn't our ultimate goal to train scientists who can apply their knowledge, and citizens who can analyze claims and technologies in responsible ways? If all we're doing is creating tests that are limited to measuring content mastery, since that's what can be measured, and then we are lowering our standards to meet mandated passing rates, aren't we actually moving backwards?

Dr. P. said...


I think the content knowledge tested by the Praxis II is a prerequisite for the literacy you describe, so it makes sense to test for this content knowledge. You cannot teach students how to apply knowledge you yourself don't possess. We are moving backwards if the standards we set are too low to be meaningful, but leave people with the impression that these teachers are highly qualified.

MV said...

It is the sincerity of a teacher that makes him a good teacher.

Rebar said...

omg thanks so much for this posting!!! I just took the test and left feeling like a deflated balloon, knowing I got 4 questions wrong, being unsure of 10, and only totally confident of 70%. Minimum scores have risen, Utah now requires between 140-150 on science ones (except general science). I had no clue what my results would mean based on a 150-question test, but now I'm fairly confident I passed! I think! ;-) but more so now than with the ETS or state information, which did not break down the scoring as well as you did. I wish I could give you a hug!

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