Slightly OT, but highly relevant to my career and generally related to this board. A recent NY Times blog post about college students surfing the net during class caught my eye. Written by Yale law professor Ian Ayres, it addresses the issue as to whether students should be allowed to browse online while in a lecture class. It's a tough topic, but one that I have been forced to think about and form opinions on, as it is relevant to my own classroom experiences.
Personally, I allow internet browsing, under certain circumstances. I see it as identical to sleeping, doing the crossword puzzle, or day dreaming in class. No, the student is not going to learn as much if they are not paying attention, but that is not my responsibility. It's theirs. If they want a good grade, surfing is not going to get them one.
Here is where I start to put limits on the surfing: if it is distracting other students. In the same way I ask students to stop talking during lecture, or when I wake up a student who is snoring, I do ask students to stop playing on their computers if what they are doing is distracting either other students or, frankly, me. And I tell them why I am asking. I literally stop lecture and ask them to cut it out because it is distracting. They usually do and often come down and apologize after class. And I accept the gesture.
This has not really been an issue yet, but I would also tell students I do not want them to surf in a seminar-type class where participation is crucial and respect for fellow students comes first. Surf all you want when I am talking. I am getting paid to do this, and I have enough tough skin to not take the behavior personally. But when a student is brave enough to express an opinion, that person deserves attention and respect. Blow me off all you want -- your grade will suffer, and that is the consequence. Do not blow off your colleagues. That is not OK. Ever.
Sometimes, however, a computer in the classroom is a good thing. People ask questions I can't answer (gasp!). Then there is some research-data-computer-addicted person there to save the day (see this Doonesbury comic also referenced by Ayres). We all just need to make sure that the answer provided is from a reliable source. I use this teachable moment to talk about why we would trust the answer being provided by the site. Students don't think about the quality of their references often enough. This helps them think about polishing that skill.
Bottom line is that students have always come to class and then never paid attention. If you can't deal with that fact -- don't teach. But we also need to consider how the method of not paying attention is affecting the rest of the students. Because they are who comes first. Build rules around that and I bet your classroom environment will be conducive to learning. Just not everyone will take you up on it.