Here's a related official example from our district:

http://www.seattleschools.org/UserF...ssionid=387f1c9b56ba0467eec5adaf9a4e1c92

(I'm not endorsing any of the viewpoints above)

Dr Hertzog is a professor at the University of Washington. There's no research data for any of her points in this presentation but maybe it can serve as a starting point if your looking for more info.