Everyone agrees that the most important in-school factor in student achievement is the classroom teacher. At the same time, however, everyone has a different proposal for reaching that goal. Rather than recite the entire list, I'd like to examine one recommendation more closely.

Although alternative routes are now available for licensing teachers, the vast majority of teachers still come from the nation's schools of education. In light of the criticism leveled at the caliber of their graduates, it's time to ask if they should be overhauled. If so, then the question is what should they look like?

This point was raised on Jul. 21 when the National Council on Teacher Quality released its report titled "Student Teaching in the United States" ( "Training of Teachers Is Flawed, Study Says," The New York Times, Jul. 21). The study examined 134 student teaching programs across the country and concluded that three-quarters of them did not meet five basic standards for high quality.

Even if the findings are open to question, the fact is that student teaching is the single most valuable part of teacher preparation. As a result, it behooves reformers to ask what can be done to remove any doubts - and there are many - about the quality of existing programs.

Consider the following conclusion: The schools differed so widely in their curricula, methods of assessment, and graduation requirements that it was impossible to know with any degree of certainty if students were being well educated. Although powerful changes were transforming some schools, the outlook was utterly hopeless for two-thirds of them.

If you thought this was a criticism of education schools today, you'd be wrong. Actually it came from the landmark Flexner Report in 1910 that evaluated medical schools across the country. (I wrote about this subject in a Commentary published on Sept. 16, 2008 in Education Week.)

The Flexner Report was commissioned by the American Medical Association, which created the Council on Medical Education in 1904 to investigate ways to restructure the existing system of educating doctors. The council in turn asked the Carnegie Foundation for the Advancement of Teaching for help. Its president chose Abraham Flexner to head the study because of his experience as a professional educator. Flexner pulled no punches. He labeled the California Medical College "a disgrace to the state whose laws permit its existence" and Chicago's 14 medical schools "the plague spot of the country." See Thomas Neville Bonner's Iconoclast (The Johns Hopkins University Press, 2002) for further details.

As a result of his report, medical education underwent a metamorphosis. Reformers are asking why the same transformation can't happen in teacher education. It's a perfectly good question, but there are several practical considerations to bear in mind.

To begin with, there are 3.2 million public school teachers, as compared with 954,000 licensed doctors. Despite the growth in the number of accredited medical schools (Virginia Tech Carilion is the newest), there are still only 133 in existence compared with 1,400 schools of education. How likely is it that we can turn out enough highly qualified teachers on the required scale? I doubt that quality and quantity are possible.

Take the example of Finland, which is widely considered to have the best schools in the world. It makes admission to its education schools extremely competitive. Only 10 percent of candidates who apply are accepted, and they come from the top of their classes. But Finland is able to maintain these rigorous standards because it has a total population of only 5 million. Once again, quantity is a crucial factor.

Another consideration is that medicine is predominantly a science, whereas teaching is primarily an art. As a result, it's easier to establish agreed-upon criteria in the former than in the latter. By its very nature, art is a virtuosic endeavor that largely defies quantification. It's seen by experts as a gift that cannot be taught in the same way that science is taught.

There's one final factor. It has to do with timing. The release of the Flexner Report coincided with the zenith of the Progressive movement. But any analogous report about schools of education has to contend with the ascendancy of the free market movement. Based on the enormous clout that billionaires wield over education in this country, I wouldn't place much hope on an impartial study.