All It Takes Is One ...
I have long believed that the time on-task lost to disruption and behavior problems is almost certainly one of the under-discussed root causes of the achievement gap. This study does a great service by confirming what many teachers and parents have intuited for years: disruption matters and has a negative effect on all students.
Clay Burrell draws attention to the policy implications:
The study seems to seriously undermine the validity of any attempt to evaluate (and pay, retain, and promote) teachers based on their class performance on standardized tests.