High-quality professional development should consist of at least 50 hours per year, and it should focus on teachers’ specific content areas, she said. It also should involve teachers in studying and collaborating on exemplary lesson plans, then implementing these plans—supported by coaching and modeling—and reflecting on their success.

To do professional development correctly, she said, schools must find the time for teachers to build lessons collaboratively. Teachers also should be looking at student work together, developing common rubrics, and scoring work together, so they have a common framework for what constitutes high-quality work.

“The more teachers collaborate, the more we see the work of teachers as collective, the greater student achievement will be,” she said.

But how teachers are evaluated can either facilitate or impede this process, Darling-Hammond cautioned: Evaluation systems that rank teachers according to value-added formulas—in other words, systems that “foster competition instead of collaboration”—will actually undermine success.

Teacher evaluation systems should take into account how much educators contribute to the school’s culture as a whole, and not just their own classrooms, she said—something that high-performing school systems (like Singapore) often do. They should include group goals as well as individual goals.

Value-added models are too volatile for district leaders to rely on as a means of assessing teachers, she said, citing examples of teachers who have been rated highly one year and poorly the next.

The number of students who live in poverty, speak English as a second language, have special needs, or even who excel can vary widely for teachers from year to year—and this can have a profound effect on how a teacher scores according to value-added rankings.

Follow Editor in Chief Dennis Pierce on Twitter at @eSN_Dennis.

For more coverage of AASA’s National Conference on Education, see:

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