States should create "alternate routes" to becoming a teacher. Colleges should require future teachers to major in a field other than education. These are two of the scores of reforms of teacher education that have been put forth in the last 20 years.

They might be good ideas, and they might not be, at least as far as what research suggests. That was the message of the editors of a 730-page book, Studying Teacher Education, which was released Monday by the American Educational Research Association. The book was prepared by a panel of education researchers that spent four years reviewing all the existing research on teacher education and summarizing it.

In many sections of the book, the most striking thing is that the sections on what research has found emphasize the many questions on which there is no definitive evidence. In fact, the authors of the book see its significance as much as setting an agenda for future research as for what it reveals about what has been found.

"We think people have been asking the wrong questions," said Marilyn Cochran-Smith, co-editor of the book and the John E. Cawthorne Chair in Teacher Education, at Boston College. She said that an emphasis on "which is better?" research (comparing two approaches on any number of issues) has resulted in tons of studies that fail to link the entire process of education. Research tends to focus on one question, she said, failing to go far enough to see whether particular approaches to training teachers actually result in better teachers in classrooms.

Some of this may be inevitable. Education students aren't lab rats, and education researchers can't randomly assign identical students to take different kinds of training and then place them in truly identical schools to see the impact. And some teacher educators noted that other professions have similar limitations, and are able to arrive at a consensus that certain things are indeed wise to do -- for instance, "Do we randomly assign medical students to take anatomy or not?" said Susan Fuhrman, dean of the Graduate School of Education at the University of Pennsylvania.

But despite that example, Fuhrman said that she was bothered, as a dean, about how little definitive research exists. "Given what we don't know, we should be much more reflective about our programs," she said. One thing she said she would do, and that she hoped other deans would do, would be to collect more data on their graduates -- where do they work, what kind of experiences do they have, what kinds of measures of success do they find?

The book was released at a time of considerable debate over teacher education. Congress is gearing up to review the Higher Education Act, and teacher educators are aware that lawmakers have used previous reauthorizations to bash their programs and impose new regulations. At the same time, more for-profit providers of higher education are moving into teacher education. (The scholars who worked on the book said that there was no reliable comparative data on the success of for-profit and nonprofit programs, or on the relative success of public vs. private institutions.)

The book is organized into sections based on research topics, such as research on arts and sciences courses, research on methods courses, research on preparing teachers to work with students with disabilities, and so forth.

Much of the discussion at a briefing on the book focused on the research that remains to be done. Despite the concerns about unanswered questions, researchers pointed to some positive signs. Kenneth M. Zeichner, co-editor of the book and associate dean of the School of Education at the University of Wisconsin at Madison, said that one of the most important recent trends in education research was that more people in other fields -- economics and political science, for example -- are doing it.

He said that he hoped these scholars would be attracted to the research challenges outlined in the book, which focus on tracking specific education approaches to long-term impact in schools.

And while the book repeatedly notes the need for more research, it also offers a sense of issues on which there is a research consensus about teacher education. Many of these findings concern demographics and specific characteristics of programs. Among the findings:

• Most new teachers are prepared as undergraduates at public colleges.
• An increasing number of teacher education graduates also major in non-education fields.
• College graduates in secondary education programs have comparable SAT/ACT scores as other students.
• Close collaboration between schools of education and local school districts appears to have a positive impact on teacher preparation, as evidenced by the performance of graduates.
• In one field -- mathematics -- there is conclusive evidence that subject matter training and certification of future teachers has an impact on subsequent teacher performance.

Information about ordering the book, along with its table of contents and other background information, is available on the AERA Web site.