The typical student standing in line this week to register for classes at Montgomery College and Prince George's Community College is not a teen-ager recently finished with high school but a woman in her 20s, probably married and with children.

According to school administrators, women will make up 57 percent of the enrollment this year at Montgomery College and 60 percent at Prince George's, and, on average, they are 18 months older than the men students. More than two-thirds of the total enrollment at both schools will be students older than 20, administrators said.

Dorothy Kiley, who is attending Montgomery College along with her 20-year-old daughter, will only give hints about her age.

"I'm the mother of three children--the eldest is 20--and I was no child bride," she said, as she waited to register for classes. She is reluctant to give her age, she said, because after five semesters "I still don't know what I want to be when I grow up."

Community colleges always have had their share of older students, but during the last decade the average age of students taking classes for credit at Montgomery College's three campuses in Germantown, Rockville and Takoma Park has risen from 24 in 1974 to nearly 28 this year.

"It's not the colleges but the world of work that has changed," said Virgil Dykstra, Montgomery College administrative vice president. With the Washington area's economy increasingly reliant on service-related and high technology industries, Dykstra said, "There are still a lot of people who don't have the skills they need to function in the work place. We have to ask ourselves who's going to train them if we don't."

Professors say the older students--more serious and career-minded than their younger counterparts--are positive influences in the classroom. "They're over certain kinds of inhibitions, and they challenge the younger kids," said Phil Mancha, a Montgomery College history professor.

Last semester, Mancha was leading a class discussion about the Depression, when one of his students, a 76-year-old retiree, gave the class an eyewitness account of the 1932 "Bonus March" on Washington by penniless World War I veterans.

Older students say they get along well with their young classmates, although there is sometimes an adjustment period. "The first day of classes they don't know quite what to think of me, and they are slightly subdued," Kiley said. But once homework and exams set in, students of all ages find plenty of things they have in common, she added.

"If you're open and outgoing and can share in some humor, it helps break the ice," Kiley said. "It also helps if you ignore things you would not ignore as a mother."

Charlie Bugg, 45, who has been taking classes at PGCC in Largo, said his experience has helped change his mind about teen-agers. "I've been the oldest one in all my classes, but the young people have been just beautiful. It's shown me that not all young people are bad. You hear about all the drugs and trouble kids are getting into but anyone who thinks all kids are like that should just come down here at night."

A print shop supervisor at the Government Printing Office, Bugg said he began studying business management to keep up on his job.

"The younger people coming up are better educated and better able to compete for jobs and promotions," he said. "I need additional education for writing reports. I need to know how to find information."

As a counselor at Montgomery College, Bill Patterson said he sees four general types of older students: people taking classes just to increase their knowledge, people trying to get ahead in their current jobs, those who are looking for career change and women looking for a new career after raising their families.

Gaithersburg resident Bill Gamer, 69, a recently retired certified public accountant, signed up for a computer course at Montgomery College's Rockville campus last week. He said he may do some substitute teaching in the future and wants to keep up with trends in his field.

"I'm interested in getting a second specialization," said John Skilton, 36, who is taking accounting classes at PGCC. Although he has a doctorate in psychology from the University of Maryland, Skilton said he began studying accounting after getting interested in the business aspect of his, D.C. consulting business. "It keeps me academically fresh," he said.

But the fastest growing segment of the community college population is women. A decade ago, they made up 48 percent of the enrollment at Montgomery and Prince George's community colleges; now they are in the majority on both campuses.

"Most of the women are going back to school because they are in a transitional phase," Montgomery College counselor Nancy Winer said. "They're either going though a divorce or they've raised their children, so if it's not a crisis, it is still a big transition."

Pam Slusher, 36, said she went back to school to have something to supplement her income and something "to fall back on." Like thousands of other area students, Slusher hopes to cash in on the demand for computer training.

Robert Hardwick, director of planning and administration at Prince George's Community College, said the demand for courses in high-technology is growing faster than the college's ability to keep pace.

The number of students taking computer classes at Montgomery College doubled from 2,200 in 1981 to an estimated 4,400 this year. Hardwick said Prince George's expanded its computer facilities 20 percent this year.

Class size, location and price are the keys to a communty college's success, Hardwick said.

Prince George's Community College charges only $27 a credit hour and Montgomery College costs $30 a credit hour for county residents. In comparison, the University of Maryland charges $113 for the first credit hour and $64 for each additional hour.

By offering popular job-related courses in addition to traditional education at prices students can afford and at locations convenient to their homes, Dykstra said community colleges will be among the few institutions "that don't have to wonder what their job is or where to get students in the future."