Bill Gates highlights the reasons he opposes releasing the data in this NYT op ed:

LAST week, the New York State Court of Appeals ruled that teachers' individual performance assessments could be made public. I have no opinion on the ruling as a matter of law, but as a harbinger of education policy in the United States, it is a big mistake.

I am a strong proponent of measuring teachers' effectiveness, and my foundation works with many schools to help make sure that such evaluations improve the overall quality of teaching. But publicly ranking teachers by name will not help them get better at their jobs or improve student learning. On the contrary, it will make it a lot harder to implement teacher evaluation systems that work.

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