Julianne Ams, a brown-haired second-grader, returned from her first day of school in 1989 giving no sign that she had just begun a bizarre educational experiment. Her math and science classes at Great Falls Elementary had been taught in Japanese, a language she did not know, but she acted as if that were no more unusual than playing tag at recess.

Her mother, Nancy, mystified by such nonchalance, questioned her. How was it? Did you understand anything?

There were words she did not understand, she told her mother, but the teacher used hand gestures and she learned something.

Today Julianne is a senior at Thomas Jefferson High School for Science and Technology, fluent in Japanese, learning Spanish and Russian and thinking about a career in international law. Yesterday afternoon, she and many of the 320 other students who inaugurated Fairfax's language-immersion program attended a ceremony at Fairfax High School to mark its 10-year anniversary.

They were celebrating not only their own linguistic achievements but the remarkable growth of the language-immersion approach. When Fairfax launched its program at eight elementary schools, only two other Washington area schools had such a curriculum. It is now offered at a total of 28 schools in Fairfax, the District and Montgomery, Prince George's, Anne Arundel, Arlington and Prince William counties. Nationwide, the percentage of elementary schools using immersion jumped from 2 percent to 8 percent from 1987 to 1997.

In the typical immersion program, children spend half the day learning English and social studies from a teacher speaking English, and the other half of the day learning science, math and health from an instructor speaking the foreign language. Teachers use gestures, pictures and educational toys to help students absorb the new language as they learn to multiply and divide and tell the difference between Mars and Venus. Fairfax has programs in Spanish, French and German as well as Japanese.

"It took a while for me to understand what was going on," said Kime Hill, a Herndon High School junior who started French immersion in first grade. But by the beginning of second grade, Hill said, she was comfortable using the language.

In Fairfax and other school districts, students completing the elementary program take accelerated foreign-language classes in middle and high school. Hill has taken advanced high school French courses and hopes for a career as a sportscaster, using her fluent French as she travels the world covering events such as the Olympics.

A decade ago, the idea that parents would want to immerse their children in a foreign language--at an age when they were still trying to learn how to read and write English--seemed far-fetched to many educators.

But the voluntary programs have proved quite popular. Many parents have wanted their children to have the early exposure to a foreign language, so they can learn the language more easily and enhance their job prospects in a global economy.

Educators say the approach is one of the only ways for U.S.-born students to achieve a high level of proficiency in a foreign language.

Moreover, schools in communities with large concentrations of Latino immigrants are increasingly using classes alternating Spanish and English to help Latino children overcome the language barrier--a form of bilingual education that avoids political controversy. Immersion programs at schools such as Arlington's Key Elementary have roughly equal numbers of children who speak Spanish and who speak English at home, and the students help each other.

Many of the students who were language-immersion pioneers in Fairfax say their academic and career plans can be traced back to those elementary classes.

Stephanie Gepford, a Herndon High junior, remembers ordering crepes aux fraises in Paris two summers ago. She speaks French with her sister Katie, also an immersion student, and wants to major in linguistics in college. "This program opened everything up for me," she said.

In a speech prepared for yesterday's anniversary event, Langley High School senior Jessica Karr said the immersion program at first seemed frightening but has given her unforgettable memories. "In the sixth grade, I was chosen by teachers to present a short speech in Japanese and a gift to the emperor and empress of Japan" when they visited Washington, she said.

At Langley, Japanese teacher Suga Carney pushed Karr into competing in the Japan Bowl--a contest of language and cultural knowledge--and attending two intense summer programs for Japanese speakers. Hoping for a career in international business, Karr has discovered that Penn State University will give her automatic junior standing based on her language skills.

Research on the long-term academic effects of immersion programs is sketchy. But studies in Fairfax and elsewhere have found that the instruction does not hurt students' scores in English, math or science.

Regla Armengol, one of the original teachers in the Fairfax immersion program, said she appreciates the linguistic skills that early exposure to foreign languages produces. But the biggest thing to her is that it means exposure to a foreign culture as well.

"They begin to understand and get away from a myopic view of the world and see it as a mosaic with a lot of different pieces," she said.