I know Haidt and his recent work on the subject has been mentioned recently a few times on here. I came by this Ed talk he did last fall. Worth a watch/listen.
For those already afflicted with ADD... Here's a couple shorter interviews.
Jonathan Haidt Wants You to Take Away Your Kid’s Phone
The social psychologist discusses the “great rewiring” of children’s brains, why social-media companies are to blame, and how to reverse course.
www.newyorker.com
Bottom line...
No phones in schools
No smartphones before high school
No social media until age 16.
Only works if other parents in your sphere are also bought in. Basically every parent of my 9 year olds group of friends have committed.. Will see how well it holds up as they get older. Some of the parents have older kids and have regrets how they handled this issue with their olders.