Timothy Jones happily bid his freshman year farewell and reveled in the fact that he no longer would be a member of the youngest high school class.

But when Timothy, 15, becomes a sophomore next week , he'll relive one of the hardest parts of freshman year: being the new kid in school. Last week , Timothy registered at Northwestern High in Hyattsville after transferring out of a high school in the District.

"I'm just really looking forward to doing better than how I was doing in D.C. schools," the Hyattsville resident said. "I really want to start off good."

Timothy won't be the only new kid on the block when classes resume, nor will any of the other new students spilling into the county's nearly 200 schools.

Many of the new faces appearing in Prince George's schools will belong to adults: about 55 new principals, 45 new vice principals and 850 new teachers. There will also be a new crop of central office administrators, the result of schools chief Andre J. Hornsby's reshuffling of his management structure.

"[Fourteen] months into this, it was time for me to come up with my final organization," said Hornsby, who took over the 137,000-student system in June 2003. Hornsby said he took his time evaluating his staff to determine who should be in charge.

Hornsby has made no secret of his willingness to reassign principals who have not improved student performance. Last summer, he demoted nine principals just a week before school was set to begin. This summer, about five were "involuntarily transferred," said Howard Burnett, chief administrator of human resources.

Burnett said that seven principals were promoted to central office administrative positions, and two left to work in other school systems. The rest retired, including 18 who had been working under the state's "retired rehired" program, which allowed teachers and principals to retire but return to the classroom without losing their pensions.

Most of the principals' replacements were hired from within the school system. During the past school year, several assistant principals were sent to a training program for potential principals and will continue to receive mentoring throughout the year.

Not all the new principals are first-timers. Sharif Salim did not go through the training program because he had already been a principal at schools in Montgomery County and the District. Salim will start his first year as principal of Samuel P. Massie Elementary in Forestville after spending last school year as vice principal of Bradbury Heights Elementary in Capitol Heights.

"All principals are trying to meet [state standards], but beyond that I'm trying to create a culture of learning where youngsters want to read, they want to write, they want to do . . . math," said Salim, a District native who has been an educator for 30 years. "If I can build that culture of learning with parents and students, that's a major goal."

Indeed, the new school-based leaders have a challenging year ahead of them, as pressure mounts to improve student performance on standardized test scores. The pressure is due, in part, to the federal No Child Left Behind Act, which has forced school systems nationwide to change the way they go about their business. For Prince George's, that means that students can no longer be among the lowest-scoring in the state.

Most of that pressure is on Hornsby, who was hired to end the political turmoil that kept his predecessor, Iris T. Metts, occupied for much of her four-year tenure. During his first year on the job, Hornsby spent a large portion of his time trying to figure out how to tame a budget deficit that was spinning out of control. The deficit has been erased, but state legislators will continue to scrutinize the system's finances.

Now, Hornsby must turn his attention to the classroom.

"We're going to hit the ground running on day one," Hornsby said.

Prince George's students will also hit the ground running before anyone else. In an effort to add more class time before students have to take the Maryland School Assessment exams next February and March, the school board decided to start the year a week earlier than usual, two weeks before Labor Day. Most other area school districts begin classes the week before or after Labor Day.

"If you can get ahead of hurricanes, snow days, and increase the amount of instructional time . . . that's what everyone should be doing," Hornsby said.

Changing the school calendar isn't the only way Hornsby plans to get students like Timothy Jones ready for standardized tests.

To prepare students for the high school assessments that will eventually be required for graduation, Hornsby has revamped the entire curriculum. Among the changes: Freshmen will now take algebra and physics, subjects most of them would not have encountered until later. They will also spend longer blocks of time in English and math.

Timothy said he's preparing himself for the tougher pace. As a student in the District, he said, he didn't focus on his studies and let peer pressure influence him too much, and that led to multiple suspensions. "I was around a lot of bad things going on," he said.

Now, he said, he plans to pay more attention to his schoolwork. "I just have to do better," he said.

So will his new classmates, whose average SAT score did not reach 900 out of a possible 1600 last year.

But the younger students won't be spared from a tougher curriculum. Toward the end of last school year, Hornsby instructed teachers in all other grades to begin an "accelerated" curriculum. Students in the first grade, for example, began learning second grade material in the last few weeks of school while continuing to cover first grade topics. The accelerated curriculum will continue in the new school year, along with the Friday homework assignments that teachers began giving students after spring break -- yet another attempt to pack more academics in.

Even pre-kindergarten students will be expected to work harder. For the first time, Prince George's will offer all-day classes to at-risk 4-year-olds, and, as Hornsby declared last school year, they will not have naptime built into their schedule.

An emphasis on improving reading instruction will continue, with students from pre-kindergarten to the 10th grade receiving new reading textbooks in their classrooms.

The academic overhaul has led some parents and teachers to complain that the changes have been made too hastily.

"I certainly hope for a smoother year than last year," said Carol Kilby, president of the Prince George's County Educators' Association, the teachers union.

But school officials say last year's changes were well thought out and necessary for a system that has historically trailed its neighbors in student achievement, despite recent improvements in Maryland School Assessment test scores.

"We can't continue to operate that way," Hornsby said.

There are other challenges beyond student achievement.

For one, the county is still trying to figure out how to deal with an expected high school enrollment boom. By 2006, the school system could be as many as 9,000 high school seats short. The County Council and the school board have disagreed over how to make room for the students. Hornsby and the school board argued that building a new high school and expanding six existing high schools was the most expedient solution.

Council members agreed to build the high school and expand one school but formed a task force to decide whether expanding the remaining schools would be wise. Instead, they have argued, the school system should build a second high school.

At the same time, the system is beginning the phase-out of many of its magnet programs. In February, the school board voted to eventually eliminate unsuccessful magnet programs from 33 schools as part of its settlement of a decades-old desegregation lawsuit. It will also expand, over the next four years, those magnets that have had rising test scores, such as the French immersion program.

Many students will also shift schools this year as part of the latest round of boundary changes. Since the system began returning children to their neighborhood schools in 1998, about 14,000 students have been moved. Additional rounds of boundary changes are expected over the next two years.

But getting past the first few days of school is what is first and foremost in the minds of most parents and school administrators. After all, there is a new school to open up: Port Towns Elementary in Bladensburg.

For Frances Weekes, mother of soon-to-be first-grader Cameron, there is another intensive year to prepare for.

Throughout the summer, Weekes made sure that Cameron, a student at Carrollton Elementary in New Carrollton, regularly read books and watched educational videos. She did phonics drills with him.

Cameron is ready for school, she declared last week. She's not so sure about herself.

"I'm not ready," Weekes said. "The summer hasn't been long enough. Mom is not ready for homework."

Port Towns Elementary's Lisa Farabaugh, above, one of 55 new principals in the county school system this year, leads a teacher training session at the school. At right, three of Port Towns's new teachers, Charles White, from left, Rodney Carter and Angela Oates talk in the media center during a break. They and other Port Towns faculty are part of a "Resident Teacher" program at Howard University, for people moving into teaching from other careers. Below, Port Towns teacher Kim Oliver already has her board decorated.Teachers Emily Little, left, and Kim Oliver unload supplies for their new positions at Port Towns Elementary. Both taught at Rogers Heights last year. About 850 teachers will assume new positions in county schools this year.