From La Costa to Carmel Valley, the ring of school bells Monday morning signaled the end of summer for thousands of San Dieguito Union High School District students.

At San Dieguito's five high schools and four middle schools, Monday was the first of 180 instructional days appearing on a school calendar that shows June 12, 2008, as the final day of class.

For many students, that date seemed a long way away.

On the first day of his senior year, Brad Vorce, 17, found the bright, horizontal light of early morning somewhat foreign. Brad said his summer wake-up time was somewhere between 10 a.m. and noon.

"Go out late, come home, sleep, and do it all over again," was how he described his summer routine.

Brad and the rest of the district's nearly 12,360 students can look forward to one-week breaks in November and April and a two-week break in December.

Officials said Monday that enrollment patterns in the 85-square-mile district are flat or, at some schools, declining. State reports show La Costa Canyon's enrollment was 2,532 last school year; enrollment on Monday was estimated at 2,450.

In response to the decline, officials this summer ordered the removal of eight portable classrooms. Crews shipped them to San Dieguito Academy, where eight other portables needed replacement.

The bell that sounded at 7:45 a.m. at La Costa Canyon marked a milestone for Brian McPherson, 14, a freshman who said he was starting high school a bit sleepy. The restless night wasn't because he was excited but because the mosquitos were biting, he said.

Brian said he had misplaced his cell phone and was beginning his high school career with no personal electronic equipment.

All around him, though, students gabbed on cell phones or trudged to class with headphone wires dangling from their ears.

Monday also was momentous for Craig Lewis, La Costa Canyon's new principal, whose career as an administrator has taken him from Santa Monica to Santa Cruz before reaching La Costa Canyon earlier this summer.

"I feel really good about being here," he said.

Lewis' boss, Superintendent Peggy Lynch, said she had visited each of the district's schools Monday morning and that the day began smoothly at all of them.

"How quickly it all falls back into place, with teachers doing what they're supposed to be doing and kids back in class," she said.

For La Costa Canyon's Jen Stromm, 16, getting to class involved fighting traffic for nearly 20 minutes to reach the campus from her Encinitas home, she said.

A back-up of vehicles stretched from the school's driveway to Rancho Santa Fe Road, about a quarter-mile away.

Jen said she hadn't paid for a parking permit, so she parked the pickup she'd borrowed from her brother in the lot at Stagecoach Park, across from the school's entrance.

Once at the school gate, a shrill scream greeted her.

"Jen!" yelled three girlfriends at once, as the greeting turned into a four-way embrace.

New by the school's gate is an electronic marquee, which bore the directive: "No skateboards."

La Costa Canyon was one of several district schools that received improvements over the summer, said Steve Ma, associate superintendent of business services.

San Dieguito Academy received new paving and a new paint job; Earl Warren Middle School received a new computer lab and improvements to its track; Oak Crest Middle School's science labs got a makeover; Torrey Pines High School received a dance room where the textbook room used to be; Sunset High School received new fencing, curbs and sidewalks and landscaping is on the way, Ma said. The improvements total $2.4 million.

"We spend a good part of the year planning it all," Ma said, "then when school's out, we do a 100-yard dash."

- Contact staff writer Adam Kaye at (760) 901-4074 or akaye@nctimes.com.