Is there really a teacher shortage in this country? The usual data cited are from the U.S. Department of Education's Digest of Education Statistics. It shows that in 1970 there were 2.06 million public school teachers, or one for every 22.3 students. Today, there are 3.27 million public school teachers, or one for every 15.2 students. At first glance, these numbers seem to indicate that there is no teacher shortage and that class sizes are not too big ("The Imaginary Teacher Shortage," The Wall Street Journal, Oct. 9). But these conclusions are misleading.

First, the shortage more accurately refers to the need for 240,000 new science and math teachers in the next decade. At present, approximately 25 percent of high school math teachers and 20 percent of high school science teachers lack even a minor in their teaching field ("The Teacher Shortage: National Trends for Science and Mathematics T...," The Journal of Mathematics and Science, Vol. 7, 2004). That's not surprising because college graduates who major in science and math can earn much more in private industry than they can in public schools ("Giving Up on Math and Science Careers," The New York Times, Nov. 7, 2011).

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