The research: Both theory and practice are important

Debates over teacher training ultimately come down to a single question: Which routes produce the most effective teachers – the teachers with the most impact on their students?

Although it's difficult to definitively link individual teachers to students' achievement gains, while accounting for other factors, some sophisticated "value-added" models are beginning to do just that.

One of the most comprehensive studies so far focuses on the effectiveness of teachers in New York City schools. The teachers came from a variety of traditional university programs as well as Teach for America and the New York City Teaching Fellows program. There were also those on a temporary license.

The study found that student achievement was helped most by having a certified teacher who had graduated from a university program, had been teaching more than two years, and had a strong academic background. It also found that student achievement was hurt by having inexperienced teachers on a temporary license – something more common in high-poverty schools.

In addition, researchers identified specific elements of teacher training that tended to produce effective teachers:

•A focus on classroom work that provides meaningful experiences and has good oversight.

•The opportunity to study the local curriculum.

•A substantial amount of university course work in subjects they'll be teaching.

•A study of learning practices that could be applied depending on classroom needs.

"We'd like all programs to bypass that 'first year' effect" for teachers, says Pam Grossman, an education professor at Stanford University in California who was one of the authors of the study.

The study also found that the different programs attract different pools of teachers, Professor Grossman says. "Teach for America does minimal preparation, but they bank on selection. Traditional programs are not particularly selective, but they bank on preparation," she says.

Yet in some ways, Grossman notes, it was surprising how similar the programs are. "There's no program that's fundamentally reimagined what teacher training can look like," she says. She sees potential, though, in urban teacher residencies or high-quality master's programs that have an extensive and targeted component in the field.