Amanda Ripley, Author of The Smartest Kids in the World

Relevant quotes from an interview:

Most of the top performing countries do not routinely use tests to measure teacher performance, and the reasons vary dramatically. In Finland test data isn’t used because of the high level of trust in their teachers. Still, there are some checks and balances. The Finnish government administers tests of a sample of students around the country every couple of years to make sure achievement is up, and they share that data with principals, but it’s not used to evaluate teachers.

In South Korea, they actually expressed a strong desire to use tests to evaluate teachers but they didn’t know how to do so fairly. There is so much education going on, with so many teachers teaching kids the same subject in school as well as in the after school “hagwons,” nobody could know for sure who it was that led students to the high test score.

I think our levels of child poverty make education much harder in the US. On average, our kids are better off than kids in other developed countries, but we tend to cluster low-income kids together in one school. Our schools aren’t that diverse, and we’re one of the few countries where more resources aren’t distributed to the neediest schools.