Donna Walker has observed autopsies on gazelles at the National Zoo.

Wendell Adkins has taught juggling to third graders at Mount Vernon Elementary School.

Maegan Ahern has charted the Neilsen ratings of "The Muppet Show" for a local television station.

The teen-agers, all seniors at Alexandria's T.C. Williams High School, are part of the first program in Virginia in which high school seniors can earn credits by interning with local businesses for one semester instead of attending classes.

"These young people don't just want to glide out of high school as easily as possible," said Ruth M. Blair, program coordinator. "They realize that it's the real world out there, and they want to experience it."

They do this through a nationwide program called the Executive High School Internship Association, in which Alexandria and Fairfax County schools began participating last month. Begun in 1971 in New York City schools with funds from the Ford and Rockefeller foundations, the program now is offered in more than 25 school systems around the country.

Alexandria superintendent Robert W. Peebles is a staunch supporter of the idea. "These students go to staff meetings in the top echelons of business," he said. "They aren't there to do 'go-fer' work, like empty wastebaskets or make coffee."

Rod Clemmons, internship director for Fairfax schools, says the program also differs from college internships. "Many college students are placed in mailrooms and never get out of there," said Clemmons, who currently has 11 student interns. "Our program puts them in a managerial environment with an executive who is on the cutting edge of his or her field."

Although Arlington and other area school systems have offered part-time internships to junior and senior high school students, these are the first to offer internships to take the place of classroom work for a semester.

T.C. Williams senior Ann Czaja, an intern at the Virginia Sports Medicine and Rehabilitation Institute in Arlington, said she applied "because I figured it would be a much better opportunity than to sit in a classroom."

Czaja, who hopes to enter Syracuse University next fall as a pre-med student, said she now views sports medicine as a potential field of specialization, after experiencing the ins and outs of rehabilitating tennis elbows and football players' pulled hamstrings.

The interning, though, means a vigorous schedule. Czaja works four days a week at the clinic, from 7:30 a.m. to 3:30 p.m., attends crew practice at T.C. Williams from 4 to 7 p.m., and then works at a library from 7 to 9 p.m.

Interns operate on "an incredibly demanding schedule," said Clemmons, who has placed interns with executives at Arena Stage, the American Newspaper Publishers Association Foundation and Bloomingdale's. "It takes somebody who is really motiviated and bright--intiative-oriented, risk-taking people."

Interns spend four days a week on the job, for which they receive three credits and a letter grade. They don't get paid for their intern work.

And although they don't take actual courses with senior classmates, they are not totally cut off from their schools. Many of them stay active in extracurricular activities, and one day each week is set aside for sessions at school with their program directors.

At T.C. Williams every Monday, Czaja and the 12 other interns meet with Blair for two periods of instruction on management systems, communications and career development as well as a free-for-all discussion of their experiences. They also meet with an English teacher, who supervises the independent-study English program all interns must take to fulfill the English requirement for graduation.

Each week, the interns turn in time sheets signed by their sponsors and a daily log, which Blair calls "their personal communication on a daily basis with me." In the logs, which Blair said she relishes reading every week, the interns detail what they accomplished that day, what they learned and how they felt about their experiences.

From the logs, Blair knows that Kate Boo recently interviewed an inventor for her internship at the Alexandria Gazette, that Bill Marshall is learning the computer language Fortran at NASA's Goddard Space Flight Center, and that Donna Walker spent an afternoon learning about the breeding habits of parakeets at the National Zoo.

Tuesday through Friday, the interns are on their own, commuting to places such as the space center in Greenbelt, Md., the Kennedy Center or Capitol Hill. "They have had to make certain sacrifices, like longer days," said Blair, whose interns work a 28-hour week. "Plus they often have to spend extra money on transportation and lunches."

Blair said it wasn't easy to find sponsors for the seniors, "since in many cases they were in competition with college interns for the same slots." Also, she was adamant that no intern should take the place of a part-time, paid employe, a stipulation she carefully reviews with each sponsor.

Since she found the needed 13 businesses and the students started working, Blair said, she's received generally glowing reports about the 17- and 18-year-old interns.

At WDCA-TV 20, the Bethesda station where Maegan Ahern now works, research director Dot Stein describes Ahern as "a working part of the station. We are very busy here and don't often have time to sit down and explain everything," Stein said. "They have to be somewhat assertive and able to take initiative, which she is."

Ahern admits she is tired at the end of a long day and the lengthy trip between her home in Alexandria and her intern job in Bethesda. But "I don't miss school," she said, and added that she is glad she opted for the internship.

Ahern said her parents "at first didn't like the idea of me not going to school." Blair added that a number of parents had to be sold on the merits of having their teen-agers skip a whole semester of classroom work.

"The parents' concerns were that the student be having an educational opportunity and not doing menial tasks, plus concerns about transportation," said Blair, adding that some students' parents would not allow them to apply. "Some parents simply want their kids in school."

For any student in Alexandria or Fairfax to apply for the program, he or she must be in good academic standing--although no specific grade-point average is required--and must have fulfilled other graduation requirements.

"In no way do we want colleges to look at this and say, 'Why did a student take three units of internship when they needed other courses?' " said Blair. "We want this to be a plus."