FOR THE KIDS CHEERLEADING : Sideline Sport : Being on the squad means a lot more than chanting rah-rah. Most girls are trained dancers who undergo rigorous training.

When 120 girls at Rio Mesa High School signed up for cheerleading tryouts this month, they knew it wouldn’t be just their vocal cords, spunk and school spirit under scrutiny.

Cheerleading is a sport now, their coaches say, and it is as physically rigorous as any other sport. No longer are cheerleaders simply rah-rah girls on the sidelines rooting for the home team. They are dancers, acrobats, gymnasts--stars in their own right.

Some squads even participate in state and national cheerleading competitions, giving their members a taste of personal glory.

“Years ago the girls were there just to pump up the crowd,” said Lois Bustard, Rio Mesa High School pep squad adviser and English-physical education teacher. “But now it’s more showy and splashy.”

Perhaps Bustard got the largest turnout ever for tryouts this year because of her girls’ success at competitions. They placed seventh in the country at the National Cheerleading Assn.’s competition in Dallas in December, 1989. Last December, they competed again, making it to the finals but not placing in the top 10.

If cheerleading has gotten more physical, it’s also become more complicated. Bustard has two varsity squads: The song leaders perform high-energy dances in a clipped style that resembles a Michael Jackson video, and the cheerleaders do tricky aerial maneuvers and pyramids. Along with two other teams, freshmen and junior varsity, she has 39 spots to fill.

Her squads are all girls now, but during two previous years she had three male cheerleaders. One had been a football player who joined the squad at the end of the season.

If there ever was a thought that male cheerleaders were sissies, it was dispelled the first time the boys performed for the school.

“They did back flips across the floor,” Bustard recalled. “All the students were standing up yelling.”

To build up their strength, they worked out with weights. Each was so strong, she said, that he could lift a standing girl over his head and balance her on one hand.

Most of the girls on Bustard’s squads have had years of dance instruction, and it shows. “You have to have it to be good at those moves,” she said, watching her song-leading squad work out with would-be cheerleaders before the tryouts.

Laura Brown, a 17-year-old Rio Mesa song leader, has studied dance for nine years.

“That’s what I want to do,” she said of her goal of becoming a professional dancer. Brown so impressed the instructors at NCA’s summer cheerleading camp at the UC Santa Barbara last summer that she was named All American Cheerleader. She has been asked to join the staff this summer.

Bustard, as well as many other cheerleading advisers, requires her girls to attend the four-day camp at their own expense. With the cost of one or two uniforms, the total expense can be as much as $450.

Bustard also demands a fair chunk of their time.

“In August, they are mine,” she said. They practice every day for about three hours. Then when school starts their gym class becomes a daily cheerleading workout. Two afternoons a week, they practice two hours after school. Then they must perform at the games.

There are other requirements, too, all included in a contract the girls and their parents must sign. They have to maintain good grades. In fact, the grade point average for varsity members is 3.6, she said. Parents must get involved as well. They are required to work during school fund-raisers.

When the girls were preparing for competition, the heat was on in more ways than one.

“We fund raised our brains out to get to Dallas,” Bustard said. They performed for service clubs and received donations.

The girls felt the pressure of performance jitters. “It was a very stressful experience getting ready, but the payoff was great,” said Suzannah Underwood, homecoming queen and varsity song leader.

Competing has given them something they didn’t have before, she said. “We’re not just cheering for the football team. We have our own niche, our own competition. It’s made us more like athletes.”

There are several cheerleading organizations that sponsor competitions regionally and nationally, the largest being the NCA. About 500 schools were represented at the cheerleading association’s national competition last December. Not all high school squads in Ventura County participate in competitions, and only a handful vie at the national level.

Simi Valley High School’s squad, preparing recently for its tryouts, has been competing the last seven years. In January the team won the regional competition for the United Spirit Assn., and placed in the top 10 at the national competition in Irvine in March. The junior varsity squad took top honors last year at a state championship at Magic Mountain.

The school takes its cheerleading seriously. The girls lift weights, run at least a mile every day after practice and build stamina on stair-climbing equipment.

“Cheerleaders used to get up and go rah-rah,” said Janice Kratz, advisor to the squad. “These girls are athletes. They can tumble. They can build stunts. They’re probably the most physically fit on campus because they go all year round.”