A Los Angeles Times series that rated thousands of elementary school teachers based on their students' average test score gains rattled the education world -- including many who study teacher effectiveness for a living.

At the core of the provocative newspaper report is a new method of teacher evaluation with an esoteric name -- "value-added" -- and a complicated statistical formula. This measurement is designed to estimate the average progress a teacher's students made during a given school year, compared to other teachers, as captured by standardized tests.

The Times analyzed seven years of student test data for teachers in grades 3 to 5 and assigned 6,000 teachers rankings from 1 to 5, from "least effective" to "most effective." Teachers whose students showed greater improvement than others, on average, received higher rankings.

The nation's education secretary, Arne Duncan, endorsed the Times decision to publish the names and ratings of the teachers, saying parents have the right to know if their child's teacher is effective. But some, including noted UC