At the SXSW conference, I was lucky enough to see many great presentations. One that I found interesting and relevant to education was called Using Twitter to Improve Student Engagement. The presenter, Rey Junco who is an Associate Professor of Academic Development did two studies involving college students and twitter.
In the first study which had tight control, 125 first semester PreHealth students were taught about either Twitter or Ning to enhance their courses. Twitter and Ning were used

• to increase time on task
• as a way to ask questions
• to discuss common readings
• to formulate study groups
• to see campus events
• to organize service learning project

Both groups had no prior experience with their assigned platform. For the Twitter group, one class twitter account was created so that students could follow each other and follow their teachers and engage with the course materials.

From this experiment Junco reports that Twitter students pulled teachers into their feeds more and engaged with teachers more. There were over 3800 tweets and the level of introspection was better when students were in the 140 character limit of twitter. Statistically, the twitter group was more engaged +5.53 versus 2.29 for control group. The grades of Twitter users were also better 2.79 versus 2.29 for the control group on Ning.

In the second study students were taught how to use twitter and they were left alone to use it. No encouragement was given by the teachers after it's introduction, and teachers did not engage with Twitter. The class was a Media and Democracy class who met two times per week. What Junco found in this study was that students did use Twitter more but the communication was amongst the class members only. It had no effect on grades, or engagement.
Junco concludes that the best thing for teachers using Twitter with students is to make sure the communication is also between the teacher and students and it should be integrated with the material.

His Best Practices are

1. Engage with the students on the platform
2. Integrate course content- make it part of the class
3. Encourage collaborative learning

Here's a short video by one of his students talking about the study



See the slideshare Presentation