Twitter and student achievement study

This research found that college students and teachers who used twitter in their course were more engaged in learning and earned higher grades than parallel students without the Twitter inclusion.
R. Junco, G. Heiberger, E. Loken (2011) The effect of Twitter on college student engagement and grades, Journal of Computer Assisted Learning, 27(2),119-132.
http://www.biojobblog.com/uploads/file/twitter%20as%20an%20educational%20tool.pdf

Public school distance education report

A majority of public school districts in the United States have students who participate in distance education courses at some level, according to data released by the National Center for Education Statistics. But the most of those districts aren't delivering the education themselves.
National Center for Education Statistics. (2011). Distance Education Courses for Public Elementary and Secondary School Students: 2009–10. Washington, DC: Author.
http://nces.ed.gov/pubsearch/pubsinfo.asp?pubid=2012008