I think the author has a great point - the one I like most - which is - when someone is invested in their school, they usually are more focused on their education.

Public schools have to take everyone. And, right now, there seems to be too much emphasis on teaching to the test.

For some teachers, they may choose to take the lower salaries to be in a smaller classroom where they usually have more control over their curriculum and where the families are more involved in the school. And where they don't have to invest all their teaching energy on those very kids who don't care because their performance/job depends on that.