Eric Van Aart stands with a knapsack slung over his shoulder and peers out from under his longish blond hair, scanning the audience of students at Hardy Middle School in Northwest Washington.

Eric is making his debut with "The Kids on the Block," a family of puppets that was born six years ago as a tool for educating the public on physical disabilities, including blindness, deafness and cerebral palsy, but has since branched out to speak for other areas of social concern.

Eric has joined Valerie Perkins, a lively 14-year-old on crutches who has spina bifida and wants to be a cheerleader; Mark Riley, 12, a red-haired boy with cerebral palsy who is in a wheelchair; and Joanne Spinoza, 14, whose main problem is self-doubt.

Created in Washington, "The Kids on the Block" have taken their performances throughout the nation and to 15 countries abroad, and many cities have started their own versions of the program.

But Washington is still "the hospital where all the kids are born," their creator Barbara Aiello said; all the puppets are still researched, tested and assembled in this area.

The puppets come in sizes from 3 feet tall to adult height, each with a complete biography, a birthdate, family, friends and past experiences that they recount to the audience. They use real wheelchairs and canes and prosthetic limbs.

Behind them, the puppeteers, dressed in black, are fully visible to the audience as they manipulate the puppets, in the manner of bunraku, an ancient form of Japanese puppetry. The "Kids" sing, dance and chatter their way through several skits each performance and usually focus on what is different about one or another member of the group.

In the opening skit, Valerie and Joanne are waiting to try out as cheerleaders when Joanne poses the question probably on the minds of most youngsters in the Hardy school audience: how can Valerie be a cheerleader when she is dependent upon crutches and leg braces? And what are the crutches and braces for anyway? she adds.

Valerie responds with a simple explanation of spina bifida, comparing her braces to poles people use to support tomatoes growing in their gardens. She then demonstrates she is, in fact, a very appealing cheerleader who gets enthusiastic support from the audience with her "Pork Chops, Pork Chops, Greasy, Greasy: We can beat your team, Easy, Easy!"

The candid and humorous exchanges between the characters indicate that, unlike the images projected on television and in movies, disabled people are neither superhuman nor pathetic; they're simply people with differences.

The puppet characters admit their limitations and frustrations, but they also are quick to demonstrate that their disabilities are not as limiting as people might think.

The puppet family increases by six to seven new characters a year: Mark Riley has a twin, Michael, who represents the sibling of a disabled child; Diane Delaney, 11, has leukemia; Brian McDaniel, 12, is epileptic; Steven Arthurs, 9, is physically abused by his foster family; and Jinx Braxton, 12, is a gifted girl who is teased by peers about her academic abilities.

Aiello developed the idea for the puppet family in 1977 when she was a special education teacher. About the same time, a federal law that entitled disabled children to be educated alongside other students took effect.

Aiello said she was looking for a way to make it easier for disabled students to move into regular schools. She saw the difficulties her former special education students were having and decided the solution was to "educate the nondisabled majority." Public law, she said, "can set circumstances but cannot mandate attitude change."

Although the puppet outfit resembles federally funded, nonprofit programs, it is a thriving small business, as the performance prices and cost of buying the puppets reflect. Local shows cost $350, and kits containing two to six puppets range from $1,400 to $3,400. The company grosses $750,000 a year, most of which is plowed back into research and development of new puppets and programs, Aeillo said.

She said she decided on a profit-making business because "a lot of wonderful programs for and about disabled kids have come and gone all too quickly because of the ebb and flow of federal funding."

Nancy Reagan, who has been active in helping children with drug-abuse problems, sent two aides for Eric's debut at the Hardy school--press secretary Sheila Tate and projects director Ann Wrobleski.

The seventh-grade audience, at first cautious in their questions, asked Eric about his rehabilitation. One girl wanted to know if Eric began using drugs "to be one of the gang?" Another student wondered, "How many joints does it take to get high?"

The puppets have an advantage over adults as an education tool, Aiello said, because they are a nonthreatening source of information and do not represent authority, although they have knowledge.

Bernard Posner, executive director of the President's Committee on Employment of the Handicapped, said puppets allow children to "let down their guard and ask brutally honest questions . . . they normally wouldn't dare ask" about handicaps.