On a recent weekday morning, Rick Robb was curious to find out how many students in his freshman English class at River Hill High School had read the story he assigned them -- the tale of a sniper in Northern Ireland. So Robb asked them whom the sniper kills at the end of the story.

But instead of raising their hands and waiting for him to call on one of them, the students typed their answers on folding keyboards connected to palm-size computers, which sent their replies directly to Robb's laptop at the front of the room.

The computers, worth $750 each, have been lent to all 580 freshmen in the school by a McLean-based company called Mindsurf Networks Inc. Within weeks, Robb said, 150 teachers will be using the computers in their classes -- making River Hill one of, and possibly the largest, public school-based wireless network in the country.

By using them in class, Robb, who is managing the school's computer initiative, said he is able to gain a far better sense of his students' knowledge and skill level.

"Without the computer, five kids would raise their hands, I'd ask one, they'd get it right and I'd have no idea how many kids actually knew the answer," he said. With the computers, "every kid has a voice; kids can't hide at the back of the room. . . . This individualizes instruction and provides immediate feedback. That's revolutionary."

Mindsurf, which provides educational software and technological support to schools, has been using River Hill to test its software since last year, when the company gave Palm Pilot personal digital assistants (PDAs) to 15 freshmen as a pilot program.

The devices' computing power quickly proved too limited, so the company switched to hand-held computers. Unlike a PDA, a hand-held computer can run regular computer software such as Microsoft Word, allowing students to peruse reading material and instantly look up words in the text that they don't understand.

Teachers can also use the network to refer students to Web sites, audio clips and work sheets, as well as to spreadsheets tracking students' grades. Each student also has a "digital locker" -- storage space on a server that can be accessed from the student's home computer in addition to the hand-held computer used in school.

Robb said the school asked that the hand-held computers be given to freshmen because success in high school is often determined by a student's freshman year experience.

If the response of the students in Robb's class is any guide, the program will prove popular.

"This is the most amazing thing I've ever seen," said Brad Milici, 13.

Amber Browning, 14, liked being able to type rather than having to use pen and paper. "It saves time, and my hands don't hurt," she said.

Dean Kephart, Mindsurf senior vice president of marketing, has high hopes for the device. "I think [it] is going to be viewed like a school supply, housing instructional [material] as well as class work," he said.

"Look at the workplace," he noted. "We have moved away from paper in many cases. With e-books really growing, putting textbooks on the computer makes sense. Then kids won't be burdened with seven heavy books in their backpack every day."

One stumbling block might be teachers themselves.

"Some are resistant to change," Robb said. At first, they will have to rewrite nearly all their lessons to put them on the computer. But once they do that, the computer can save them a lot of time, he said. They won't have to photocopy lessons or grade multiple-choice tests by hand.

Then there is the possibility that students will play games on the computer rather than pay attention in class. But Robb said that teachers can prevent that by keeping a close eye on students -- something most already do.

Cost is also an issue. Indeed, the main concern students expressed was that they may lose the devices. In that event, they must pay Mindsurf $500.

"That's kind of a scary thought," said Greg Mazur, 15.

However, the school is offering an insurance program for $85, which would cover all but $40 of the cost of a lost computer.

Once their freshman year is over, students must return the devices. School officials are negotiating with Mindsurf to come up with a purchasing plan that would enable all students to buy the hand-held computers at an affordable price.

In any case, Kephart said, the devices will likely get cheaper over time. Graphing calculators, which cost about $100, are now required in many high-school classes.

Mindsurf Networks Inc. has lent 580 palm-size computers to the school.English teacher Rick Robb, right, uses a wireless computer network to quiz his students as well as to assign, receive and review assignments.