Do these results surprise anyone?
The "surprising results?" "When highly effective teachers are hired, not only do their students' test scores improve, but the scores of students in classes they don’t teach also get a boost."
Teachers become better teachers from each other, and oftentimes, teachers are inspired to try new things by just chatting with other teachers who try new things. Also, teachers can have a positive influence on their students that carries over to other classes those students have, which creates a better learning environment for all. This shouldn't be news.