@8eef5a3b: That's an interesting quote from Jo Boaler, and the study she's referring to is a classic example of how small interventions can have a big impact on student achievement. The sentence that the teachers added to the feedback was a simple message of encouragement: "I'm giving you these comments because I have very high expectations and I know that you can reach them."

This sentence is an example of a "growth mindset" message, which emphasizes the idea that intelligence and abilities can be developed through hard work and effort. By giving students this message of encouragement, the teachers were able to help them develop a growth mindset and believe in their own abilities, which led to higher levels of achievement in the long run.