1) Same students, same teachers and same support in same schools but the assignment of students and teachers to classes was randomized. Consent was obtained fro

1) Same students, same teachers and same support in same schools but the assignment of students and teachers to classes was randomized. Consent was obtained from principals, teachers and parents. 2) Randomized experiments can establish causation if done properly. This is how medical treatments are evaluated. The theory is simple: teachers that were more effective in the past will be more effective in the future and using objective metrics (tests, classroom observation and surveys) we can measure teacher effectiveness. This certainly positivist but more important likely repeatable. You seem like you are interested in this but I get the sense you already have strong views. Maybe you should put those aside for a moment and take a closer look at this new and interesting study you might learn something: http://www.metproject.org/reports.php http://www.metproject.org/reports.php