Ernestine Wright, 40, watches as about two dozen teen-agers, armed with curling irons and combs, work feverishly on mannequins' heads set up in a cosmetology laboratory at the Chamberlain Career Center.

Wright may look like a teacher, but she is just another student trying to master hair designs and make high grades. The only difference between Wright, mother of three teen-agers, and the other students is her age.

Instances of adults who, like Wright, graduated from high school more than 20 years ago taking classes with teen-agers are no longer novel in the D.C. public school system, according to school administrators. More than 450 adults are enrolled in tuition-free, daytime vocational education classes offered at the six D.C. school career centers. Most are enrolled in cosmetology, barbering, nursing, and clerical training courses, officials said.

There are about 3,355 students of high school age at the centers, they said.

In recent months, school officials say, there has been an increase in the number of adults at the career centers, where they receive the one-to-three years of training needed to qualify as laborers, managers and instructors in a variety of trades and occupations, including accounting, marketing, shoe repair, masonry and plumbing.

Any District resident can enroll in the centers at no charge. Similar training is offered at private institutions that charge tuition.

"Many of the adults are high school graduates who don't have a skill. Most are underemployed people or unemployed," said Chamberlain's principal, Paul Quander. "They can come to career centers and get the skills necessary to obtain several entry-level jobs."

For many years, career centers have offered evening "adult education" classes for people changing careers or seeking more education.

But in recent years, as unemployment has remained a problem in the District, the demand for vocational training has increased and school officials decided last year to allow adults to enroll in daytime classes. Previously, daytime classes had been reserved for high school students.

There were fewer than 20 daytime adult students at Chamberlain last year, but there are about 85 this year, Quander said. Youths are given first priority in the daytime career center classes, he said, and can acquire vocational certificates in addition to their high school diplomas under a program called "shared time," which means that they split their day between a career center and a regular high school.

Adults are allowed to fill any additional space available in the daytime classes, Quander said. A new career center scheduled to open in February in the economically depressed Southeast area is expected to attract hundreds of unemployed adults, mainly in building maintenance, building security and clerical courses.

"The unemployed and underemployed adults could be the forgotten group of people in our society right now. They need something to make them upwardly mobile," Quander said, adding that the city schools are trying to help them "attack their problems."

The training is free because the schools are public property, he said. Quander stressed that any resident of the city "should be entitled to attend our classes, if we can accommodate them."

School officials said that vocational schools across the country will be making efforts to accommodate adults and other "special populations" because the Carl D. Perkins Vocational Education Act, recently passed by Congress, stipulates that their career needs must be addressed.

Under the vocational act, more than 55 percent of $1.6 million in federal grants for vocational education must be set aside to provide training "especially" for men and women entering nontraditional occupations, as well as adults who are unemployed or seeking retraining, handicapped, poor, non-English-speaking, single parents or criminal offenders.

"Our emphasis on serving adults during the day and evening is something that the act speaks to," said Richard Rubin, the D.C. school system's chief of staff for career and adult education.

For many adults, attending school with adolescents takes some adjustment. The years separating them from their younger classmates often put them worlds apart, several said. Sometimes the age difference casts the adults in positions of role models.

"A lot of the girls look at me as their big sister," said Wright, who graduated from college in 1966 with a degree in chemistry and worked for 15 years as a laboratory technician before deciding that she wanted to be a beauty consultant.

Going to school with youths her children's age does not bother her, she said.

"I wanted to attend adult classes in the evenings, but I was told the classes were filled," she said. "There was a long waiting list and no way I could get in. I asked about daytime classes. I was told that I would be in classes with high school students. I said, 'That's okay. I just want to get my cosmetology degree.'

"I was looking into cosmetology schools in the area and they were really quite expensive. Then I found out about the career centers. I said, 'Wow, that's great.' It doesn't matter if you're taking classes with adults, senior citizens or children. I'm there to learn, so that's what I do."

Michele Brown, 25, grew up in the District, married, moved to New Jersey then was divorced and moved back with her mother. She now attends Chamberlain, studying cosmetology. Brown, who has three small children, said: "When I moved back, I tried to find a job in the civil service. I didn't have much success. I checked into going to college, but I couldn't get the money."

She said that she always has enjoyed "doing hair" so, when she discovered she could get free training, she jumped at the chance.

"And, I'm glad I did," she said.

Another adult student, William Lindsay, who "graduated from high school years and years ago" and is now "in my thirties," said that when he first started going to school with youngsters last year, "it was an adjustment period for me, having to deal with adolescents after I left that stage."

Lindsay, a cosmetology student, said he sometimes acts as a student-teacher when the instructor leaves the room and he is asked to keep everyone quiet and working.

Instructor Richard DeCarlos said: "The majority of the adults who come here have financial needs and they have their goals set. The teens are just urban kids coming in from the ninth grade. They have the normal problems and growing pains."

Pernell Wright, 16, no relation to Ernestine Wright, was surprised when he found he would be taking classes with students twice his age, but said he does not mind.

"In fact, I enjoy it," he said. "I thought career centers were just for high school students like myself, but I guess [the adults] are here because they want to learn a trade. They have to do what they have to do. Times are tough."