Poet-playwright Judith Offer believes in the future of the American musical and she is willing to put her money where her mouth is.

"What I think is that the American musical is only just starting to expand on where it is going to go," she said last week over hot chocolate and a bagel in an East Bay coffee shop.

Offer and her husband, Stuart, a tax attorney, with the help of several foundation grants, are backing the world premiere of her musical, "A Shirtwaist Tale." It opens Friday, Aug. 6 at the College Preparatory School in the Oakland Hills.

"A Shirtwaist Tale" tells the true story of how some 30,000 young — mostly Jewish — immigrant women changed the face of the labor movement by striking for shorter hours and higher wages in 1909.

The music, set to a klezmer beat, was written by Russian immigrant Arkadi Serper of Albany, a musical theater veteran in his native land. His music for the film "Luna Park" was nominated for an award at the 1993 Cannes Film Festival.

Offer, 56, a longtime educator and writer of children's plays, has been working on the musical's book and libretto for the past five years. Staged readings of the musical took place three years ago at synagogues in Oakland and San Francisco.

"I have always wanted to do a show about the immigrant experience," said Offer, who lives near Oakland's Lake Merritt. "I, myself, come from five different groups: Hungarian Jewish, Scots Presbyterian, and Irish, German and French Catholic."

Eventually, Catholicism rose to the top of the polyglot mix and Offer was raised in the religion, though she moved away from its observance in her 20s. An English teacher, she was actually working as an urban planner in Washington, D.C., when she met her Jewish husband of 29 years. The couple moved to California and had two daughters, both graduates of the College Preparatory School.

Although she never has converted, Offer considers herself "honorary Jewish." Her family celebrates the major holidays, lights Sabbath candles and holds seders on Passover.

Her research for the libretto led her from the novels of Irving Howe to New York's YIVO center for Jewish and Yiddish studies, the Tenement Museum and the Folksbeine Yiddish theater.

"I didn't know until this show that my great-grandparents spoke Yiddish," she admitted. Offer has been taking Yiddish lessons ever since.

Language fascinates her. Her poetry is riddled with made-up words that enhance the rhyme. Her lyrics have a similar kick. One song in the show is an upbeat number that satirizes the English language from the immigrants' point of view.

There is a romance, she noted, but it is not the main focus of the show.

"This subject appealed to me because, for one thing, the main people were almost all women and, for another, what they did really changed the history of labor in this country.

"I worked in a factory one summer when I was in college and I got a sense of what it's like to do the same thing, day after day. I felt so underprivileged. I think that experience influenced me a lot."

Madeleine Pabis directs "A Shirtwaist Tale," which features an onstage klezmer band — the clarinetist is a sixth-grade musical prodigy — and a mixed cast of professional and non-professional performers. Pabis, who has directed regional theater productions in New York; Cincinnati; Hartford, Conn.; and St. Louis, has taught and coached drama for the past 10 years at the School of the Arts in San Francisco.

Offer believes the show has legs and hopes it will catch the attention of producers, both locally and nationwide.

"Maybe it's not Broadway material," she said. "But off-off-Broadway for sure."