An American newspaper has taken the highly controversial decision to publish league tables rating the performance of thousands of individual teachers by name.
The Los Angeles Times will publish the rankings of more than 6,000 elementary school teachers, based on their ability to improve students' scores on standardised tests.
An American teaching union has condemned the move, describing it as "irresponsible and offensive".
The paper obtained seven years of maths and English test scores from the Los Angeles Unified School District, which is responsible for 891 schools for children aged five to 18 and a further 208 pre-school or adult education centres.
The LA Times has defended its decision to publish the database. It said the disparities between teachers' performance are known to educational officials, but "rather than analyse and address these disparities, they have opted mostly to ignore them". It argues that this means the most effective teachers go unrecognised, while ineffective teachers get no extra help.
The paper's website now includes a section called Grading the Teachers. The Times says it has decided to make the ratings available "because they bear on the performance of public employees who provide an important service, and in the belief that parents and the public have a right to the information".
Arne Duncan, the US Secretary of Education, supports the publication. "What is there to hide?" he said in an interview with the paper.
But the United Teachers Los Angeles union has called for members to boycott the paper. It claims the database dramatically oversimplifies complex education issues and will create a skewed and unfair picture of teachers.
It also complains that linking test scores to teachers' names is an intrusion into members' professional lives that will not improve students' learning.
AJ Duffy, the union's president, said: "We object to the tying of teacher evaluations to standardised tests and are supported in that belief by many prominent education experts in the U.S.
"The release of the Los Angeles Times's teacher evaluation database will create chaos in schools for parents who will be misled about their teachers. This will have a negative impact on morale in schools."
The influential McKinsey report on the world's best-performing school systems, published in 2007, pointed out that the main driver of the variation in student learning in school is the quality of their teacher.