For many of us, seeing opera as a child was an unheard-of experience, unless an ambitious teacher organized a field trip.

That's what happened when Michael Kaye was 9 years old and living in Kingston, N.Y., and he was hooked on opera for life as soon as the curtain rose on Mozart's "Cosi fan Tutte."

Now, as director of Children's Opera Theater, Kaye brings opera into the classroom - and in a way that students can even get up on stage and join in. This year, Children's Opera Theater plans to give more than 300 performances in all the public elementary and some junior and senior high schools in the District of Columbia and Montgomery County.

The schools are selected by the local school boards on the basis of a high number of disadvantaged students, lack of PTA funding for cultural activities and requests by faculty and students.

One goal of Children's Opera Theater, says Kaye, is to break through the misconception that opera is "something that exists behind a picture frame for the wealthy." Now that most of the D.C. schools have dropped music and art instruction for budgetary reasons, he considers his company's performances particularly important.

"Opera is a wedding of all the arts - musical, visual, vocal, dance, language, history, daily life in cultures not our own, comparative religion even," says Kaye. "Through opera, we can pique (students') imaginations and give them a tool to investigate all these arts."

On Children's Opera Theater's first visit to a school, four company members will introduce the students to opera terminology and history, breathing and vocal techniques, and excerpts from operas. The program is geared to the age of the students and lest attention flag, they are called on stage to sing, dance and direct.

At an elementary school, for example, soprano Myra Merritt, as Pamina from Mozart's "The Magic Flute," will prepare her audience for a tragic aria about lost love, then start singing gaily and dancing about the stage. The students jump in their seats and stop her, demanding the appropriate tears, wringing of hands and dramatic intonation.

"The point is to have (the students) discover for themselves how emotion can be explored through music," explained Kaye. "Through Pamina, they learn that even if you don't understand the language, the music gives you all the information you need."

When Children's Opera Theater goes back to a school for a second time, it will perform an abbreviated version of an opera, such as "Carmen," or "Don Pasquale."

Myra Merritt, who grew up in the District and trained at the Peabody Conservatory of Music in Baltimore, says the performing for children has helped improve her technique.

"I enjoy singing for children because they are very honest. They don't know how to hide their true feelings. If they are bored, they can't sit still," she said. "You have to be very intense and concentrate very hard, in order to pull them into what you are doing."

Kaye, who has staged operas in Boston, Chicago, Cincinnati, San Francisco, and Cologne, first developed his introductory program for children in Boston in 1973.

After a few years, he realized that this format could be used not only to expand the audience for opera, but also to provide year-round, secure work for opera singers, who usually perform only a few months a year during opera season.

In 1976, he set up shop in Washington with support from the Washington Performing Arts Society's Concerts in the Schools program and from other civic organizations. In 1977-78, the Children's Opera Theater budget soared from $30,000 to $300,000, mostly with federal funds granted under the Comprehensive Education and Training Act (CETA). He anticipates a similar budget this year.

The CETA money has enabled him to hire 23 full-time singers and production people and provide them with coaching in such fields as diction, movement and career management. With this training and the experience of performing at least three times a week, Children's Opera Theater members have move on to the San Francisco and Philadelphia opera companies and the Burn Brae Dinner Theater.

Children's Opera Theater also performs outside the schools. It has just completed a two-month series of Saturday morning performances of "Ba-taclan," an Offenbach operetta, at Wolf Trap's Little Theater in the Woods. Last spring, it presented six performances of Puccini's one-act comedy, 'Gianni Schicchi,' at the Warner Theater.

This year, Kaye hopes to give even more performances, and not for children only. He is seeking a theater downtown where a full season of three productions can be presented.

Even with this new emphasis and with a new name - the National Opera Studio - the company will continue its performances and demonstrations in the schools. Explained production assistant Helen Kamioner, "If you get a kid to like an opera, you get an adult to to like it, too."