DALLAS  Jaime Pacheco rolled out of bed at dawn last week to the blaring chorus of two alarms. Then Jaime, a 15-year-old high school freshman, smoothed his striped comforter, dumped two scoops of kibble for the dogs out back and strapped a G.P.S. monitor to his belt.

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.

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.