Dance shoes stomp, the sound made bright by nails in their soles. Ceiling fans and swirling skirts kick up a breeze in the small rehearsal room.

"Back, side, back, turn!" calls Kimberly Korinek, one of the co-chairs of Ballet Folklorico de Stanford. The dancers follow suit, both men and women buoyant. As in many performing-arts groups, the men are outnumbered. They don't seem to mind.

Ballet Folklorico de Stanford, a group of mostly undergrad and some graduate students, is an especially robust organization these days. While last year about 20 dancers signed up, this year about 40 came out. Now the group is enthusiastically gearing up for its 24th annual Concierto de la Primavera, an evening of Mexican folkloric dances from various regions.

The free performance is set for Friday, May 23, at the university's Dinkelspiel Auditorium. Also set to perform are guest groups Alma Latina Long Beach, Los Mejicas de UCSC and Mariachi Cardenal.

The Stanford group was founded in the early 1970s to promote Mexican culture on campus. The organization ran under the auspices of the school's dance department for a time, and now has been student-run since the early '90s.

"We really try to build a community more than anything," said Edgar Chavez, another co-chair of the group.

Many of the dancers were either born in Mexico or have parents who were, and enjoy taking part in an activity that teaches them more about their roots. Some are new to the art form, while others, like Stanford freshman Patricia Montes, remember trying it as a child.

The group has definitely become a community for her. "Everybody's like my second family," she said.

Ballet folklorico in its modern form is rather recent, said Korinek, whose Stanford studies include majors in Spanish and Portuguese. The late Amalia Hernandez, who founded her dance company in 1952, was highly influential in combining traditional Mexican folk dances and regional styles with ballet technique.

Polished turns mix with energetic stomp-steps, which are sometimes reminiscent of tap dance — albeit more boisterous. There are moves for both groups and couples.

On a recent Saturday afternoon, the dancers pack a small rehearsal space at the university's Roble Gym. After the women swap their full traditional skirts for shorts and leggings, the men go into the hall to practice on their own. And the women get armed. It's time for what Korinek calls "one of the few non-flirty dances," a piece commemorating the Adelitas, women warriors during the Mexican Revolution of the last century.

The women pass out plastic rifles with red tips and march with military posture. While a traditional song called "Las Adelitas" plays, they then break into lively dancing. Ponytails bounce as the dancers move, rifles held aloft.

Some of the guys have ambled in to watch, and after the song ends one calls out, "It looked good."

A girl grins and playfully brandishes her rifle at him. "You'd better say that."

What: 24th annual Concierto de la Primavera, a showcase of Mexican folkloric dances. Ballet Folklorico de Stanford, Alma Latina Long Beach, Los Mejicas de UCSC and Mariachi Cardenal will perform.

Where: Dinkelspiel Auditorium, Stanford University.

When: 7 p.m. Friday, May 23.

Cost: Free.

Info: Go to http://www.stanford.edu/group/folklorico/ or e-mail kkorinek@stanford.edu.