By 7:15, Jaime was in the passenger seat of his grandmother's sport-utility vehicle, holding the little black monitor out the window for the satellite to register. A few miles down the road, at Bryan Adams High School in East Dallas, he got out of the car, said goodbye to his grandmother and paused to press a button on the unit three times. A green light flashed, and then Jaime headed for the cafeteria with plenty of time before the morning bell.

It was not always like this. Jaime used to snooze until 2 p.m. before strolling into school. He fell so far behind that he is failing most of his classes and school officials sent him to truancy court.

©Brian Harkin for The New York Times

Jaime Pacheco, a student in East Dallas, has not missed school since being chosen by a judge to carry a device that tracks his movements.

Instead of juvenile detention, Jaime was selected by a judge to be enrolled in a pilot program at Bryan Adams in which chronically truant students are monitored electronically. Since Jaime started carrying the Global Positioning System unit April 1, he has had perfect attendance.

"I'm just glad they didn't take him to jail," said Jaime's grandmother Diana Mendez, who raised him. "He's a good kid. He was just on a crooked path."

Educators are struggling to meet stricter state and federal mandates, including those of the No Child Left Behind Act, on attendance and graduation rates. The Dallas school system, which, like other large districts, has found it difficult to manage the large numbers of truant students, is among the first in the nation to experiment with the electronic monitoring.

"Ten years ago the issue of truancy just slid by," said Jay Smink, executive director of the National Dropout Prevention Center. "Now the regulations are forcing them to adhere to the policies."

Nearly one-third of American students drop out of school, and Dallas has the seventh-worst graduation rate among large school districts, according to a study released in April by America's Promise Alliance, founded by Colin L. Powell, the former secretary of state.

At Bryan Adams, 9 of the more than 300 students sent to truancy court this year are enrolled in the six-week pilot program. The effort is financed by a $26,000 grant from Bruce Leadbetter, an equity investor who supports the program's goals. The bulk of the money pays the salary of a full-time case manager, who monitors the students and works with parents and teachers.

"I can't do anything with them if they don't come to school," said Cynthia Goodsell, the principal at Bryan Adams.

Kyle Ross, who runs the in-school suspension program at Bryan Adams, was skeptical of the electronic monitoring until he saw that it worked. "We're always yearning for something tangible to use as tools to teach self-efficacy," Mr. Ross said. "Everyone's so overwhelmed. We'll try anything."

Dallas's experiments in tracking truancy started three years ago. Last year, case managers used a G.P.S. system to locate a truant student on the verge of overdosing on drugs, and they discovered that a student had skipped school because he was contemplating suicide.

Ricardo Pacheco, 18, who is no relation to Jaime, said electronic monitoring had helped him get on track last year, despite advice from his friends to "just yank it off."

"It was easier to come to school each day, stay out of the streets and be home every night," said Mr. Pacheco, a father of two young children and a former gang leader. Now he is about to become the first male from his father's side of the family to graduate.

"They all dropped out or are in jail," Mr. Pacheco said.

Paul Pottinger, the chief executive of the company marketing the truancy monitoring system being tested in Dallas, said, "With location verification, they can't sneak through it, they can't game it like they can game their parents and game their teachers and game their friends."

©Unknown

A map showing the whereabouts of students.

Across the state, in Midland, county justice officials started using electronic ankle monitors last summer to track about 14 of the most chronically truant students. The officials hope to double the number of students monitored next year.

Truancy experts say the results in Texas are promising.

"It's far better than locking a kid up," and is cheaper, said Joanna Heilbrunn, a senior researcher for the National Center for School Engagement.

But the future of the Dallas program is uncertain. Mr. Pottinger's company, the Center for Criminal Justice Solutions, is seeking $365,000 from the county to expand the program beyond Bryan Adams. But the effort has met with political opposition after a state senator complained that ankle cuffs used in an earlier version were reminiscent of slave chains.

Dave Leis, a spokesman for NovaTracker, which makes the system used in Dallas, said electronic monitoring did not have to be punitive. "You can paint this thing as either Big Brother, or this is a device that connects you to a buddy who wants to keep you safe and help you graduate."

Jaime said he did not mind carrying the tracker.

"I'm actually happy about it, that I get another chance to do my work and catch up," he said. "I never saw myself getting held back a grade."