Dealing with the Distraction Factor

One of the things I struggle with, in classes taught in computer labs, is the distraction factor. My Journalism 2 course is structured so that students work independently and function for much of the course as freelance writers. Now I know in the real world, freelance writers work from home much of the time. They might multitask among any number of activities including reporting, writing, reading, checking e-mail, eating, and talking on their cell phones. Unfortunately, in a classroom setting that is governed by school rules much of this is impossible. In addition, watching students get done “just what they need to do” for the day to spend much of the 82 minute block playing games, commenting on Facebook, or playing videos on YouTube drives me crazy.
So the question I’d like to pose is how do you set up an environment that functions as a writers' workshop where students are productive without being distracting or breaking school rules?