Fritz the Fox and Looie the Lightning Bug are trying to coax Katy Kangaroo and Soozie the Frog into taking some of their brightly colored pills. Just as Katy and Soozie are about to swallow the drugs, Brainy Beaver skates by in time to teach the girls "the power to say NO."

Later, when the audience of second-graders from several Fairfax County elementary schools were asked what they had learned from Katy's and Soozie's experience, about 300 young voices screamed: "To just say NO!"

County school officials and federal education experts said that children are becoming more aware of drugs and alcohol at the elementary school level because of early exposure to those substances outside the classroom.

As a result, the county school system is bringing programs, such as "The Power of NO," a one-act play about peer pressure, drugs and alcohol, to its elementary school students as a way to teach children as young as 7 years old about the dangers of drug and alcohol use. Last month hundreds of Fairfax students were bused into three county high schools and the Wallace Theater in Fort Belvoir, each of which had two daily performances of "The Power of NO.". So far nearly 9,000 elementary school students have seen the play.

"We use two themes: wellness and taking care of yourself and your body. We teach about learning to say 'no' . . . call it assertiveness training," said Dennis Nelson, coordinator of the school system's substance abuse prevention program. "We don't teach the kids about heroin and shooting up in the first grade. We teach them how to make good decisions."

Nelson, who said the school system intensified its drug and alcohol abuse program three years ago, said that school officials and teachers have found that a child who is exposed to drugs at home or at the playground suffers learning disabilities and has a short attention span, among other emotional problems. He estimated that one in every 10 youngsters in elementary school is "severely affected by drug abuse in the family."

Ronald Bucknam, who has spent two years studying the effects of alcohol and drug abuse on schools and students for the federal Department of Education, said that until five years ago schools limited drug prevention programs to intermediate and high schools, where adolescents and teen-agers are most influenced by peer pressures and social cliques.

Today, he said, school systems are developing programs for children between 5 and 8 years old that emphasize nutrition and health as the way to steer clear of drug and alcohol use among preteens and teen-agers.

"These programs are part of an overall effort at changing the social climate in schools and communities to a climate that says no to drugs," Bucknam said. "We want to help the children develop a set of values so they will be part of a peer group . . . that doesn't do drugs."

Nelson and Bucknam said it was difficult to determine if 7- and 8-year-olds are really influenced by programs, such as "The Power of NO," that depict the dangers of drugs, alcohol and cigarette smoking through rock music and fictional characters.

"Check with me in 1996," said Nelson. "We haven't been doing preventive drug programs for elementary school students that long. We need to work with the students and educate them, then work to educate the school staff, parents and the community. Unless you have all those factors in place, you're not going to make a dent . . . "The Power of NO" won't do very much by itself."

The county's elementary school curriculum does not include daily lessons on good health and assertiveness, but, Nelson said, a reinforcement of the dangers of drug and alcohol comes through the use of guest speakers, schoolwide assemblies, films and classroom instruction.

"We try to constantly be giving the message that you don't need drugs to have a good time," said Nelson.

Emily M. Williams, principal at Parklawn Elementary School near the Seven Corners area, said her students are able to identify with characters such as Soozie the Frog and Brainy Beaver, and relate their experiences to those of the fictional animals.

Williams said today's first- and second-graders are more sophisticated than their counterparts a decade ago. "Children need all the background they can get for their development," she said.

Fairfax County's drug and alcohol abuse prevention program is operated under the auspices of the school system's "Ready, Set, Go for Good Health" curriculum, which includes lessons on nutrition, health, well-being and substance abuse. Nelson said the intermediate and high school abuse prevention classes include lessons on the physiological effects of drugs and alcohol and on how to identify those with a drug addiction.

"The Power of NO" was written and directed by Ronna Corman, 22, a graduate of George Mason University's theater department. It is sponsored by George Mason University and the Fairfax County Council of the Arts, which received a $6,000 grant from Mobil Oil Corp. to help pay for costumes, the set and performances by the production's five-member cast.

For more information on "The Power of NO," call 323-3587.