Alexandria school administrators have spent the summer devising a few surprises for students returning to classrooms Sept. 7.

Elementary students will get a crack at computers, sex education will be required for most ninth graders and students at the city's only high school, T. C. Williams, will attend physical education classes in a new, prefabricated gym.

High school students also can be prepared to face a tough new attendance policy adopted earlier this summer by the Board of Education.

"All in all, I would say we're ready," said Robert Harper, assistant to Superintendent Robert W. Peebles. "Bring them on."

Alexandria expects to enroll 10,250 students this fall.

Under a pilot program being started this fall, ninth grade students will be required to take a sex education course, except in cases where parents ask that their children be exempted. Any exemption request will be honored, school officials said.

The new course will focus on the entire subject of human sexuality, from the reproductive system to such topics as homosexuality and contraception, Assistant Superintendent Arlene M. Moore said.

"In past years, we've had health courses for ninth graders, but they didn't deal with subjects this course will deal with," Moore said.

The decision to start the pilot program came in February after much debate among school board members and the community. The pilot program was adopted with the understanding it could be revised before course requirements are permanently established next fall.

Alexandria also will expand its computer programs to include all elementary grades. Elementary students this year will be offered computer literacy courses designed to introduce children to computers, Assistant Superintendent Donald E. Dearborn said.

"We are one of the very few school systems in the metropolitan area that have computers in all of our schools," Dearborn said. "We've spent a year teaching our teachers how to be literate in computers, and now our objective is to make the children appreciate and understand computers."

The new elementary program will allow students to work with actual computers for a nine-week period, learning how programming works and how to use a computer to solve problems, he said.

Elementary students also will have new science and health textbooks, Dearborn said. The science text will place more emphasis on earth science, astronomy and space exploration, he said, while the health book will include updated information about health care.

Overall, however, Moore said the Alexandria curriculum will remain unchanged this year, pending a major curriculum study expected to be presented to the school board in January.

At T. C. Williams High School, the new, $855,000 gym will augment the existing gym. The facility, completed this summer, is "not deluxe" but is big enough for two indoor tennis courts or two full basketball courts, Harper said.

"I think the students will be pleased with it," he said. "It means there will be a lot more room."

In an effort to trim costs, bus service will be eliminated for high school students who live at least 1 1/2 miles from school, instead of the former one-mile limit. The change, said school transportation director John D. Johnson, is expected to save about $30,000.

High school students also will find the new attendance policy requires them to account for absences. Under the policy, students can lose credit for courses in which they have more than 10 unexcused absences.

The school board passed the controversial policy amid charges from some parents that it was too harsh.

The policy allows students to be absent for documented illnesses, religious holidays, short trips and family deaths but is designed to crack down on chronically truant students, Moore said. She said the policy will be spelled out for students and parents during the first week of school.