The idea for PTA membership drive wasn’t all wet, but the principal was.

Fifth-grader Yolyo Chan warmed up his pitching arm in a slow rotating motion Friday, warily eyeing his principal, Marjorie Van Swearingen, as she stood on the front lawn of 156th Street Elementary School in Gardena.

“Can we hit her hard?” he asked.

Fortunately for Van Swearingen, the weapons that Yolyo and hundreds of other students lobbed at her were water-filled balloons, and the shots were taken at her invitation, all in good, clean--albeit wet--fun.

As an incentive to boost PTA membership, parents came up with the idea of allowing the students from each class with 100% membership to pelt Van Swearingen with water balloons.

The incentive worked. During a weeklong drive that began Oct. 9, dozens of students coaxed a parent or relative into joining the PTA, and membership increased from an already high 90% to 109%, said PTA President Barbara DeGuire.

Some students got more than one relative to join, and a few got as many as seven or eight, including uncles, aunts and grandparents. Two classes got 200% participation--each student got more than one relative to join--and will be treated to the additional prize of a classroom pizza party.

On Friday afternoon, the PTA put up a banner across the school front reading “We Did It!” One by one, teachers led their classes outside so each student could take aim at the principal.

“Yeah, this is fun,” said Sharlena Horton, 11, just before she fired off a fastball that whizzed past Van Swearingen’s head.

“Come on, take your best shot!” Van Swearingen called to students, who squealed in delight at the opportunity to take a potshot at an authority figure.

“I think she’s a good sport,” said Celeste Sasaki, 10.

Van Swearingen said when she heard the idea, her initial reaction was, “Oh, no!”

Eventually she agreed, on the condition that she could set her own rules. Those included wearing waterproof gear--in the form of a shocking orange plastic poncho--tennis shoes and shorts. For good measure, Van Swearingen carried a racket, just in case she got a chance to lob a shot back.

Most important, Van Swearingen got to dodge and duck, making a direct hit even more of a challenge.

The real challenge was to hit Van Swearingen at all. Watching as the principal nimbly bobbed and weaved to avoid the balloons, sixth-grader Janon Hiura, 11, expressed a frustration felt by many students.

“If we could throw more than one shot, it would have been really cool,” Janon said. “I wanted to see her get really wet.”

There were several direct hits, and each brought peals of laughter from the students.

DeGuire said parents borrowed the idea from a school in San Pedro that staged a similar event last year. The 156th Street School PTA could win a $200 award for educational materials if it has the highest increase of PTAs in its district, DeGuire said.

Fourth-grade teacher Adrienne Skrumbis said the small school of about 360 students has traditionally been close-knit, and parent participation has always been high.

“I’m surprised they’re so gung-ho,” Adrienne said. “They’re always enthusiastic (about the drive), but this has been an added incentive. Obviously it worked.”

Student Celeste said she thought that the incentive program was a good way to get parents to join the PTA and that students at other schools should consider it.

“Maybe they could do other things to the principal--like throw a pie,” Celeste suggested with a giggle. “Or they could throw water ballons at the teachers.”