"Do you know who was at my house last night? Amy Carter said.

"No, who?" said Rebecca Medrano, the Spanish teacher at Stevens Elementary School.

"The President of Mexico," Amy replied.

"Did you speak to him in Spanish?"

"Oh yes," Amy said. "I asked him, 'Como se llama [What is your name]?'"

"She's gotten just very, very natural," Mrs. Medrano said last week as she talked about President Carter's 9-year-old daughter, Amy. "It's also gotten quite natural to have her at the school."

When Amy started the fourth grade at Stevens on Jan. 24 she was met by a large crowd on the sidewalk and a phalanx of reporters and photographers. The pictures they took showed a shy, worried child.

Inside the school, according to its teachers and students, Amy is a bright, animated girl, usually dressed in sneakers an jeans, doing her work so quickly and well that teachers heve sometimes told her to let other children try to answer questions first, which Amy had done without complaining.

Last week President Carter attened the school's closing assembly, and said he was happy with what Amy was doing there. A White House spokesman said Amy will be back at Stevens next fall.

"At first Amy was a little bit shy," said Verona S. Meeder, her regular classroom teacher, "but she fitted in nicely. She's also been a great positive motivater for the rest of the class. They're doing better work and mostly they're on their best behavior. She seems to have adjusted to us totally, but it's not exactly like it was before she came."

"There's a whole lot of mean boys in this school," said Juan Herron, a third-grader who is part of the Safety Patrol, "but nobody messes with Amy."

Stevens, a three-story, white-walled building, has stood on 21st Street NW, between K and L, since 1868 when it was built as the city's first public elementary school for blacks. It is the oldest school still operating in the District, but its large, high-ceilinged rooms were refurbished and carpeted several years ago.

Its enrollment - now about 215 - still is about 70 per cent black. About 10 per cent of the children are American whites. The remainder comes from about 25 different countries, mostly in Asia and Latin America, and, according to teachers, Amy's best friends in the school come from Chile and Brazil.

"It's like a real melting pot at Stevens," said Ethel Day, a Science instructor who teaches Amy and her classmates three periods a week. "It's not just of the United States, though, but of the whole world."

The student body is far from being a picked group of diplomats' children and the offspring of middle-class professionals. Indeed, about a third of the children are poor enough to qualify for a free lunch. Some of Amy's classmates are the children of welfare mothers, according to Jane Harley, the school's counselor. The parents of others, she said, include a bank teller, a key punch operator, a receptionist at a medical clinic, a cook at one embassy and an accountant at another.

Besides Amy, there are no children of important government officials in the school even thought its attendance zone includes not only the White House, but also the Watergate, Foggy Bottom and part of Embassy Row.

Despite President Carter's example, almost all high government officials living in Washington, including Vice President Walter Mondale, send their children to private schools. Indeed, the only other president ever to send a child from the White House to a D.C. public school was Theodore Roosevelt, who did it from 1904 to 1906 and then put his son in private school.

Amy's class at Stevens in a combination fourth and fifth grade with 23 students. The range of ability is wide, Mrs. Day said, with some children who have trouble reading on a second-grade level and a few, including Amy, who are several years ahead of national norms.

Mrs. Meeder said Amy reads more than any child she's ever taught in 10 years at Stevens, and is the only one this year who always carries a book with her to read on the bus when the class goes on field trips. She said, however, that Amy is reading somewhat less now than when she first came to school and was just getting acquainted with the other youngsters.

"Any test I give her Amy finishes very quickly," Mrs. Day said. "Sometimes she complains that she's all finished and wants something more to do . . . but I think she's helped her class. She's given them a model, an incentive. She's showed them good study habits, and the class has gotten much more serious about its work."

But Mrs. Day added: "Amy's not a snotty kid, she's not a brat. She's cognizant of the feelings of others. She's not snobbish. Some children dress more stylishly than she does, some dress worse, and she seems comfortable with all of them . . . She has a type of sensitivity and concern that you dont' see in a typical 9-year-old kid, but she's not some kind of martyr. If someone bothers her, she will say, 'You're bothering me, get lost.' If somebody pushes her, she pushes back."

One factor that doesn't seem to affect Amy's behavior, according to Mrs. Day and other teachers, is the Secret Service. At least one agent always sits outside the door of whatever classroom Amy is in, and agents trail behind her when she goes from room to room or about onto the playground.

As a result of its famous student, Stevens now gets regular attention from tour buses that pass slowly while sightseers peer at it. At lunch-time and recess passersby sometimes stand along the fence trying to catch a glimpse of Amy, but the onlookers now are much fewer than when Amy first came to the school. When she jumps rope with friends or swings on the metal gym bars, she seems oblivious to the attention.

Also, reporters have been kept out of the school since Amy arrived there, except for a few assembly programs. However, after McCall's Magazine printed an article about Amy by Mrs. Meeder in its June issue, Mrs. Carter's press office gave permission to a Washington Post reporter to do a story, provided he didn't try to interview Amy. The school system also gave its permission, provided Amy's classes were not disturbed. Both conditions were respected.

Stevens has been different this year, however, not only because of Amy, but because of an unusual all-day program, which started in September four months before Amy arrived.

As part of the program, some children arrive at the school as early as 7:30 a.m. and eat breakfast there. They can stay as late as 6 p.m. Altogether, about 170 of the 215 youngsters at Stevens are involved in the program, including about 80 who live outside the school attendance zone but whose patents work in offices nearby. Five of the youngsters live in the suburbs and pay tuition.

Over the past decade the enrollment at Stevens, once as high as 700, has declined sharply as the row houses, alley dwellings and light industry that used to make up its neighborhood gave way to office buildings, parking lots, and expensive apartments. Mrs. Harley said there were only 145 children at the school last year. She said the all-day program was started to attract others and save the school from being closed.

The $42,000 it costs to run the all-day program comes from federal anti-poverty funds, funneled through, the D.C. Recreation Department and a Neighborhood Planning Council. The program qualifies for the funds, Mrs. Harley said, because it employs 25 low-income teen-agers and young adults as its aides.

There are no restrictions on the family income of the children who take part in it, and Amy stays late four days a week, not only for the Spanish lessons but also for classes in photography and computer programming.

Since Amy came, Stevens has had some unusual programs, including a visit by performers from Ringling Brothers circus, a folk dance group from Georgia, and a dance group from the Russian embassy school. It also had an alumni day for the first time in its history, and Mrs. Meeder's class visited the training camp of Muhammad Ali and toured an art gallery with Rosalynn Carter and the wife of the President of Mexico.

The class has made one visit to the White House - to have its own Easter Egg hunt on the lawn. A few children, Mrs. Meeder said, have been invited there by Amy to bowl, see movies, or play. She said one girl, Claudia Sanchez, the daughter of a cook at the embassy of Chile, has stayed at the White House overnight.

Last week a few children complained that Amy was getting special treatment, and a few parents and teachers said the many special programs had interfered with regular classwork. Most, however, thought Amy was being treated like other children and thought the school was either much as it had ben or better since she was there.

Mohammed Zafar Qureshi, an accountant at the Pakistani embassy, has twin daughters in Amy's class, Naumana and Shandana.

Since the president's daughter is here," he said, "people feel much better about their school because their own school seems important. But Amy doesn't act like she's important. She plays with my daughters, she talks to my daughters, and the teachers treat her like they treat my daughters. When they have to pick up their own chairs, Amy picks up her own chair. It's democratic."