Phoenix - Earphones on, eyes on the computer screen, the ninth grader types the word he hears: I-M-I-G-E-S. Wrong, the computer tells him. He tries again: I-M-U-G-E-S. Still wrong. He starts the next word. T-E-C-N-O-L In a flash of frustration, he leaves the spelling program and clicks into a reading drill, where he correctly answers questions about the Blue Man Group, and then, calmer, he returns to the spelling program.

Across the room, some of his classmates are at other computers, some are sprawled on beanbag chairs reading to themselves, and some are at a table where the teacher, Mari Bailey, is teaching how to paraphrase.

It does not look particularly revolutionary. But the reading classes at Cesar Chavez High School are part of a new breed of high-intensity efforts to deal with adolescent illiteracy, one of the toughest problems facing urban high schools.

In Phoenix, about two-thirds of the incoming ninth graders read at least a year below grade level. And the statistics from other cities are similar. That reading lag, experts say, is largely why almost every big-city school district has at least twice as many 9th graders as 12th graders.

Thousands of high school students are held back each year because they cannot read well enough to absorb information from their textbooks. Many spend several years in 9th and 10th grade before dropping out, never becoming fluent readers. In New York City, Schools Chancellor Joel I. Klein said recently that 36 percent of 9th graders and 43 percent of 10th graders were forced to repeat the grade last year.

Susan Frost, president of the Alliance for Excellent Education, a private research group, cited data from the federal Department of Education's 2003 reading assessment, showing the extent of the problem.

"Right now," Ms. Frost said, "nationwide, 25 percent of the students arriving in ninth grade are unable to read well enough to take high school courses, let alone rigorous courses to prepare them for college. If you want a predictor of who will leave before 12th grade, it's those 8th-grade reading scores."

In the last few years, however, almost every urban school district has begun experimenting with programs to bolster adolescent literacy. Further research is now under way to determine which approaches work best.

"For 20 years, everyone was saying you have to teach kids to read by the end of third grade or they're lost," Ms. Frost said, "but now what the research is showing is that teaching them to read, to decode words, isn't the same thing as teaching them how to use reading, how to have the fluency and comprehension and vocabulary they need."

There is, of course, a problem of priorities. Most educators, and the federal No Child Left Behind act, still stress the goal of teaching young children to read, and most districts focus on the youngest children, not the adolescents who have fallen behind. The Phoenix Union High School District has been able to put adolescent literacy at the top of its agenda because it is made up solely of high schools.

"If we were a K-12 district, would we be putting all this energy and investment into the 9th and 10th graders," asked Jean Anderson, the district's curriculum director, "or would we be putting our money in the early grades, and writing the high school kids off like everybody else? I don't know."

In the Phoenix district high schools, 3,600 9th and 10th graders with low reading scores now spend a double period, 110 minutes a day, in a program called Read 180, rotating through activities intended to help them develop reading comprehension and fluency. They tend to be students who have never liked reading, never read for pleasure and never had much sense of academic success. All of them started the year reading below the eighth-grade level - but many are now catching up, some jumping two grades in reading in just one semester.

"I was getting C's, D's and F's last year, and at the beginning of this year, I was having a bad time," Angelica Osornio, a ninth grader, said. "But now I'm getting A's and B's. This class is really increasing my ability, and I'm liking school more."

And Angelica recently reached a milestone. She picked up a book for fun. "I'm reading 'Go Ask Alice' at home," she said. "It's interesting."

Some students say they particularly like the computer drills because they are individualized, allowing them to go at their own pace and make mistakes in private.

"I used to be the one always asking how do you spell things," said Juan Avalos, another ninth grader. "You feel stupid. Now people come and ask me how to spell things. Doing spelling on the computer is my favorite part of the reading class."

Juan said his progress was so noticeable that his English teacher singled him out as one of the most improved students in the class.

Until recently, there was little in the way of research, financing or specific programs to help educators tackle adolescent illiteracy. But these days, there are dozens of programs.

While every model is different, many train teachers to read aloud to demonstrate techniques for active reading. Instead of simply plowing through a book, the teachers help students focus on comprehension by stopping frequently to review what they just read, to predict what will happen next, to flag unfamiliar words or muse aloud about the questions the text raises.

In many school districts nationwide, literacy is infused into every subject area, so that even a high school math or history teacher, introducing a new unit, would first give students new vocabulary words, post them around the room, and assign students to define the terms in their own words.

Last year, Phoenix began requiring each of its high schools to focus on such literacy strategies.

But the centerpiece of its effort is the $3 million program for struggling readers it brought into the high schools in September, Read 180, named for the 180-degree turn in literacy it tries to promote.

"There are lot of programs out there that we looked at, but we had a hard time finding anything as comprehensive as Read 180," Dr. Anderson said. "The best way to teach reading is one on one, but with thousands of kids that's not practical. This is the next best thing. We keep the class to 24, and they're divided into three groups, so the teacher can work with eight kids, knowing the others are gainfully employed."

These are still early days for the Phoenix reading program - and officials there are quick to caution that there is no silver bullet for adolescent illiteracy.

Still, the early results are impressive. More than two-thirds of the 10th graders in the program last semester had higher reading scores after four months - and 24 percent had jumped two or more grade levels.

But not everyone is enthralled. "It's boring," confided Jacalyn Lopez, a 10th-grade reading student at Carl Hayden Community High School. "You're on the computer every day and nothing ever changes. I tried to get out of it, but my counselor said I needed to take it."

Ted Hasselbring, who was then co-director of the Learning Technology Center at Vanderbilt University, developed the program years ago under a federal Department of Education grant on how to use computers in teaching reading.

"In 1993, the Orange County public schools in Orlando, Fla., called us and said they had behavior, truancy and dropout problems with kids who couldn't read, and we did a pilot program with them," said Dr. Hasselbring, now a professor of education at the University of Kentucky. "After one year, we found that the kids in the program came to school more, their grades went up, their behavior improved and, partly because they started at such a low level, they averaged two to four years' reading growth."

Read 180, now owned by Scholastic, supplies software that tracks each student's results on all the computer drills, provides lesson plans for teachers and keeps a library of short easy books that even poor readers can get through on their own, along with harder ones that students can read while listening to an audiotape featuring the voices of a narrator and a reading coach who pops in with comments and questions about the text.

Teachers in the program receive analyses of students' performance on the computer drills and where they need further help. That individualized instruction is the key to the program, said Ernest Fleishman, Scholastic's senior vice president for education.

"Parents don't go into a store and say, 'I want a fifth-grade shoe,' " he said. "There's no such thing. And there's no such thing as a fifth-grade book. The kids in one class may be reading at eight different reading levels, which makes it very difficult for a teacher, without some kind of program like this."