Bill Gates makes the claim that Masters degrees don't increase the ability of teachers in his TED talk.
What are the characteristics of this top quartile? What do they look like? You might think these must be very senior teachers. And the answer is no. Once somebody has taught for three years their teaching quality does not change thereafter. The variation is very, very small. You might think these are people with master's degrees. They've gone back and they've gotten their Master's of Education. This chart takes four different factors and says how much do they explain teaching quality. That bottom thing, which says there's no effect at all, is a master's degree.
Is this true?