For teachers, engaging a large classroom in limited time can be a challenge. For students, speaking up may be a intimidating. That's why more and more professors are looking to use what is usually a distraction as a teaching tool.

Purdue University is experimenting with an application called Hotseat. It uses Facebook, Twitter and Text messaging so students can comment and exchange questions in real-time. When class is over, the conversation continues.

The University of Texas in Dallas had a similar experiment with Twitter that showed more student participation. "What I have seen is that nearly every one participates in some way," said . "Either in class, or on their computers, or cell phones, or they do the handwritten comments and give them to the TA. And she posts them after class is over."

And after class is over the discussion doesn't have to stop. Dr. Rankin used this Twitter account with hashtags to engage students. Several studies show that greater participation translates into a better academic performance, and Twitter can help overcome a shyness barrier.

"Trying to pipe up and be heardyour opinion is out there for everyone to read," said Dave Schallert, a freshman at the University of Texas at Dallas.

Dr. Rankin says there are some downsides. Students are limited to 140 characters per tweet, and students who don't have a device to access Twitter can't participate in real-time.