Alarm clocks and school bells will ring earlier this year for most of Loudoun County's 14,900 students as the school system adjusts to a new schedule brought on by the addition of an extra high school class period.

The high school day will change from six class periods to seven, allowing students to take extra courses. High school students will begin their day at 8:40 a.m., 12 to 18 minutes earlier than last year, and end at 3:20 p.m. Class periods will be slightly shorter.

The change in the high school day will affect most of the county's middle and elementary school students as well. Opening and closing hours will vary slightly from last year, in order to keep middle and elementary school bus schedules synchronized with high school bus schedules. The school system has notified parents of the new schedules.

The county is switching to a seven-period day after last year's pilot program at Park View High School in Sterling.

"We had a real positive experience with it," said Park View Principal Kenneth Culbert.

"Kids could expand their opportunities . . . . They could take additional courses. Kids who had . . . fallen behind could catch up sooner that they would with six periods."

Park View students last year chose from the same course offerings as their counterparts at Broad Run, Loudoun County and Loudoun Valley high schools; they just took an extra course or study hall.

But this year's high school students can choose from an expanded course list as the school system begins offering a host of new classes for the first time.

Among these is a course in discrete mathematics. Loudoun will be the only school system in the state to offer this course to all 11th- and 12th-graders who have taken two years of algebra and one year of geometry.

Previously, the course has been offered only at the Thomas Jefferson High School for Science and Technology, a magnet school in Fairfax County that is open to gifted students from around Northern Virginia.

Larry Farmer, the county's instructional supervisor for math and science, described discrete mathematics, which includes probability, statistics and logistics, as a tool students can use to solve practical problems.

What is the most efficient way to distribute the mail in the Pentagon? How do electrons course through a supercomputer? How does the U.S. military move hundreds of thousands of troops and supplies to one desert country half a world away?

"Right now I'm sure {the military} is doing a lot of discrete math," Farmer said.

He said he and the county's math instructors have been talking about adding a course in discrete math for several years. He's excited about the upcoming year.

"We're constantly learning new ways to use numbers," Farmer said. Discrete math is "as practical as addition and subtraction, as necessary to mathematical literacy as add, subtract, multiply and divide were 30 years ago."

Besides the discrete math course, high school students can take a course devoted solely to probability and statistics, which Farmer calls "subsets of discrete math."

They can also take psychology, international relations, post World War II American history, guitar, Asian studies, etymology (the study of the origin of words), history of minority groups in America and Latin American studies.

Middle school students can take two foreign languages, Latin and German, in addition to the previously offered French and Spanish.

Elementary school students will not have new courses, but will use new textbooks for spelling and handwriting.

All students who buy meals in the school cafeteria will pay more this year.

Breakfast, served at some schools, will cost 70 cents, 10 cents more than last year. Lunch will cost $1.25 for elementary students and $1.30 for middle and high school students, 25 cents more than last year. Adults will pay $1.90, 30 cents more than last year.

At Loudoun County High School in Leesburg, students will return to a $6.5 million renovation and expansion project that includes a new wing housing eight modern science labs and a larger cafeteria. By late September, there also will be new music and band rooms in the old cafeteria space, a new computer lab and classrooms in the former science wing, air-conditioning throughout the school, an upgraded electrical system and renovations to administrative offices and the library.

Richard Johnson, assistant superintendent for support services, said the renovation is the largest in Loudoun County High School's history. The school, built in the late 1950s, is the oldest high school in the county.