Simone Posey spent part of the weekend searching her wardrobe for the perfect outfit to wear on her first day in eighth grade. She finally settled on blue jeans, a red jacket and a white T-shirt adorned with a heart and the word "sweet." Then she finagled a pair of red Nike sneakers from her older sister.

The carefully selected ensemble aside, Simone, 12, said she didn't feel ready for the first day of classes yesterday at Thomas G. Pullen School in Landover. After all, her last day of seventh grade was June 18. And here she was, two months later, getting ready to trudge out of her family's Upper Marlboro home to catch a school bus.

"I just don't want to go," she said, barely taking her eyes off the Nickelodeon channel as it flickered in her bedroom. "I didn't get a vacation."

With Labor Day two weeks away, students in Prince George's and Frederick counties returned to public schools yesterday while their counterparts across the Washington region embraced the final days of summer vacation. In Calvert County, where classes resume today, make that final hours.

All other area Maryland public schools will reopen Monday, and District students will return Sept. 1. Schools in Virginia are required by law to start after Labor Day, though Fauquier County qualified for a waiver to open Aug. 30 because its school system has historically lost a large number of days to snow cancellations.

It wasn't too long ago that school districts across the country waited until after Labor Day to unlock their doors. Not anymore. With standardized test scores increasingly determining a school's success or failure under the federal No Child Left Behind law, many districts are starting classes earlier in the summer to give students additional time to study before state exams.

Waiting until Labor Day, or even a week before the holiday, would be far too costly to Prince George's students, said county schools chief Andre J. Hornsby. Despite recent improvements, Prince George's students generally have scored lower than their peers in neighboring counties on the Maryland School Assessment tests. So this year, Hornsby urged the school board to start classes a week earlier than usual.

The early start gives teachers more time to cover material their students will need to know when state testing begins in early March, Hornsby said, while providing a cushion against weather-related cancellations, particularly snow days.

Hornsby and the school board also changed the way semesters are set up. The first semester will end before students depart for winter break, rather than in January. That way, Hornsby said, they will be more likely to remember material that appears on end-of-semester exams.

"We're shifting our children to a college way of life," he said.

But even college students get to enjoy longer summers, some parents argued.

"I think children really, really need that summer break, and the parents do, too," said Tone Martin, whose son started sixth grade at Thomas Pullen yesterday. "I know I do."

The change in the school calendar wasn't easy on teachers, either.

"The reality of it hit hard when you realize, 'My vacation's over,' " said Maryann Fox, a Spanish teacher at the school. Yet Fox said it was necessary, because testing is high stakes these days and the amount of material to cover is extensive.

Loretta White, the principal at Thomas Pullen, agreed. She greeted her students with smiles and hugs yesterday but also reminded them that work would begin right away.

"At this time, all cell phones must be turned off," White said over the public-address system during first period. "Please prepare for morning announcements."

Simone Posey started preparing the night before. She went to bed at a reasonable hour Sunday -- before 11 p.m. -- but awoke at 2 a.m. and couldn't get back to sleep, she said. She watched "Three's Company" reruns and cartoons until it was time to get ready for school about 7 a.m.

A fan of to-do lists, Simone scribbled down her morning routine and taped it on a wall near her bedroom door. There were the usual items: "Brush teeth." "Wash face." "Do hair." "Clear mascara." Then there was a first-day-of-school goal: "Meet people," she wrote.

Once ready, Simone joined her parents in the kitchen, but she didn't want breakfast. She sat in a chair, her shoulders slumped, her face looking glum, clutching her Scooby-Doo lunch pouch, which her mother had filled with a plum and cold pasta.

"Buckle down, kid. The party's over," her father, Alonzo Posey, told her as he skimmed the newspaper.

Starting school early makes sense to Simone's parents. "I wish they would start a week earlier," her father said. "The problem is they have too much idle time."

Simone frowned. "We only got two months off," she said.

"I wish I could get two months off," her father responded.

A short bus ride later, Simone walked into Thomas Pullen, still moping, especially when her mother, Cynthia Mason-Posey, decided to accompany her to school. "It's that 12-, 13-year-old thing," Mason-Posey said. "She doesn't want to be seen with her mom."

The sour look on Simone's face disappeared when she spotted her friends. There were many hugs and comments on each other's outfits -- bright yellow and pink sneakers, and T-shirts emblazoned with statements such as "I'm out of bed. . . . What more do you want?"

Simone squealed with laughter when she learned that she was in the same science class as one of her closest friends. Suddenly, starting school didn't seem like such a bad thing.

Simone and Chelsea Harris, right, greet each other like long-lost friends.Before her first day in eighth grade, Simone Posey talks with her father, Alonzo, in their Upper Marlboro home. "Buckle down, kid. The party's over," he said.At the John Hanson Montessori School in Prince George's, Corrine Massey lines up her class of first-, second- and third-graders. Calvert County schools open today, and other area Maryland districts will begin classes Monday.