NEW YORK — When Don Herzog, a law professor at the University of Michigan, asked his students questions last year, he was greeted with five seconds of silence and blank stares.
He knew something was wrong and suspected he knew why. So he went to observe his colleagues' classes - and was shocked at what he found.
"At any given moment in a law school class, literally 85 to 90 percent of the students were online," Professor Herzog says. "And what were they doing online? They were reading The New York Times; they were shopping for clothes at Eddie Bauer; they were looking for an apartment to rent in San Francisco when their new job started.... And I was just stunned."
Wireless Internet access at universities was once thought to be a clear-cut asset to education. But now a growing number of graduate schools - after investing a fortune in the technology - are blocking Web access to students in class because of complaints from professors.
Herzog first went on the offensive in his own law classes, banning laptops for a day as an experiment. The result, he says, was a "dream" discussion with students that led him to advocate more sweeping changes.
This school year, the University of Michigan Law School became the latest graduate school to block wireless Internet access to students in class, joining law schools at UCLA and the University of Virginia.
The problem professors face is "continuous partial attention," an expression coined by Linda Stone, a former Microsoft executive, to describe how people check e-mail and try to listen to someone at the same time.
"As a teacher, you can tell when someone is there, but it's just their body that is there," says Douglas Haneline, a professor of English literature at Ferris State University in Grand Rapids, Mich. "Their face is on 'screensaver,' so to speak, because what they are really doing is checking their e-mail."
Like most professors, Mr. Haneline wants to be flexible about computer use in class. At the same time, when it comes to holding face-to-face discussions about a poem, he wants to see a student's face - not a laptop screen.
A growing number of professors now want computers - not just the Internet - out of class. Two professors at Harvard Law School have independently banned laptops in their classes, and many other law professors around the country have done the same.
For some, the issue comes down to learning styles. Professor June Entman of the University of Memphis Law School in Tennessee says some students with laptops end up typing every word said in class.
"When you focus primarily on transcribing everything said, you are not making good use of the class as a practice opportunity," she wrote in an e-mail to her law students, explaining her decision to ban laptops.
Law school students say laptops are good for taking neat notes and e-mailing them to friends who miss class. Laptop notetaking is still largely a graduate-school phenomenon, but the practice will probably spread to undergrads - unless teachers balk.
"It would have upset me if they had banned computers at Michigan," says University of Michigan Law School student Michael Jacobson. "I think my laptop has enhanced my study skills in that I'm able to capture a lot of what's said during class."
Educational assets aside, the main issue for graduate students with banning technology is their freedom - the freedom to use a tool that can be useful in class.
"If [the] Internet is distracting in law school," wrote second-year Harvard Law student Bryan Choi, "it will be just as distracting in the real world, and if Internet is helpful in the real world, it can be just as helpful in law school."
The UCLA Anderson School of Management realized the futility of blocking Internet access last year. In 2004, when it began offering wireless, it installed blocking devices in classrooms. Last year, however, the school decided to remove the block.
"We all came to realize that if students wanted to communicate electronically, they could do so by hooking up their cellphones to their laptops or by just text messaging," wrote Susan Gutman, an official at the school. "In some ways, student behavior is the same as it ever was. In the old days, they chatted with each other, passed notes, read the newspaper, or did other work in class.... Now they surf, IM, and e-mail or play solitaire. The issue is behavioral."
Supporters of computers in the classroom emphasize useful ways that computers can be used in class, such as a program that lets professors ask questions of students and receive responses electronically to see how well they understand a lecture.
Professor Steven Smith, a psychology professor at Texas A&M University in College Station is "delighted" when students use laptops in class to access lecture outlines posted on course websites.
This may be the wave of the future. According to one recent study by the Campus Computing Project, more than one-quarter of university campuses have campus-wide wireless networks. That portion grew from one-fifth in 2004 and only 3.8 percent in 2000.
As wireless Internet access expands on campuses, the next frontline for laptop use may be undergraduate classrooms, where, for whatever reason, most students still don't use them in class.
"Every single person I have ever seen bring a computer to class has also surfed the Web or been on IM," says Amy Kornell, an undergraduate at the University of California at Davis. "I saw one girl watch a whole episode of 'Gray's Anatomy.' But I would guess that solitaire is the most popular game."