As a young "Rough Rider" in the early 1960s, she had walked the halls of Roosevelt High School, toting a load of books and wondering about her future. Back then, Sharon Pratt was surrounded only by her fellow students.

Yesterday, Mayor Sharon Pratt Dixon, surrounded by security guards, advisers, school officials and reporters, returned to her alma mater for the first time since taking office in January.

She was met at the door by an honor guard of uniformed students and given a tour of the Northwest Washington building. Teachers greeted her warmly. Students gawked. Searchers failed to turn up a 1961 yearbook that would have shown the future mayor among 221 graduating seniors. The book was missing from the school files, possibly lifted by a Dixon admirer.

While cameras clicked and tape recorders whirred, Dixon stood in front of a blackboard in a crowded basement classroom and told humanities students that the discipline and self-confidence she learned at Roosevelt had helped propel her into the mayor's job.

"You are what you believe you are," said Dixon, who staged an upset victory last fall over better-known rivals.

In a 20-minute lecture covering a basic theme of Black History Month, Dixon told the students what happened as she finished MacFarland Junior High School and prepared to enter nearby Roosevelt, at 13th and Upshur streets NW.

The MacFarland counselors had assessed Dixon's potential, based in part on her spotty academic performance.

"The assessment then was that I didn't really have it," Dixon said. "The assessment was that my family ought not to pressure me, beause I just didn't have what it takes."

But, Dixon said, she resolved to prove the assessment wrong.

"In my first year, because I hadn't exercised my mind, I studied five and a half hours a day, and I was a C student," she said.

She kept studying and was a B student by 11th grade. By her senior year, she was an A student and was elected class president.

"When I set out to become mayor, people thought it was amusing," she said. "People slammed the door in my face. I called them on the telephone and they never answered my phone calls."

But, she said, she had learned to believe in herself.

The mayor delivered her message almost like a sermon, rarely looking at her notes and frequently underscoring her remarks with a sweep of her hands. When she finished, she offered to take questions.

Jocelyn White, an 11th-grader, went first: Was it wise for Dixon to try to save money by cutting back on spending for education?

Dixon gave a qualified "no", saying she wants money channeled into the classroom but doesn't want it wasted on administrative overhead.

Duane Thomas, a 12th-grader, and Olive Cox, an 11th-grader, both wanted to know about statehood for the District.

Dixon predicted that it's coming. "Within five years, it's very real," she said.

When Principal Robert Gill told the class that Dixon had to leave, after she had answered only three questions, the mayor appeared surprised.

"I guess she got so caught up in speaking that she didn't realize the time was all gone," said Sonja Sims, a Dixon spokeswoman. "She was disappointed she couldn't listen to more questions."

Some students also expressed disappointment that there wasn't more time for questions.

"I expected her to talk and let us ask questions the whole period," said Jumoke Davis, a senior. "We got a half-hour." The class runs 90 minutes.

Davis said he had hoped Dixon would offer more practical advice. "Most people who come here try to say motivational things," he said. "I'm kind of tired of people talking and not really doing anything."

Other students gave rave reviews of the mayor's performance.

"She is an inspiration for all black women," said Marsha Forrest, an 11th-grader. Forrest said she wants to become a lawyer but feared her B grade average wasn't good enough.

Having learned that Dixon was once a C student, Forrest said she will renew her efforts to bring up her grades and enter law school.