A Kensington nursery school that was a pioneer in this area in cooperative education--where parents share in management and classroom activities in exchange for lower expenses--is fighting to survive in an economy where both parents in an increasing number of families work during school hours.

The Kensington Nursery School, founded in 1939 as one of the first cooperative centers for preschool age children in the area, operates morning and afternoon programs that can accommodate up to 50 children.

But enrollment has slipped in recent years and stands at 35. School officials and parents said the cooperative approach doesn't have the appeal it once had because so many mothers have gone to work. Four parents help the co-op's director and two teachers with two daily classes.

At the same time, the Kensington school also is unusual in that it owns its land and building, which opened in 1957 and was designed by a participating father who was an architect. Most of the area's approximately 30 cooperative nurseries are located in churches.

But maintenance of the Kensington building, at 3202 Decatur Ave., has become a worry. The roof had to be replaced a few years ago, and the "furnace may go next. . . . We have a tenuous financial situation," said Silver Spring resident Kathy Rushing, vice president of the co-op.

Rushing, whose 4-year-old daughter, Jessica, is the third child in her family to attend the school over seven years, is an editor at the National Audobon Society. She said she has found cooperative schooling a "major source of my friendships" and a parenting experience that "puts your own child in perspective. . . . It's a microcosm of the real world."

A co-op nursery school is an "option that ought to be around . . . . I feel like it's home for us. The next year I'll automatically drive to the nursery school first," she added.

About 30 co-op nursery schools are in the metropolitan area, with most of them in churches.

Throughout its more than 40 years, more than 750 families have sent their children to the school, and at least one parent of each family has worked one day a week at the school.

Judith Barker, the school director and teacher for the 3-year-olds' class, describe Kensington Nursery as not academically oriented. "The children are lacking social skills at this early age, and we help them to get along with other children and adults, helping to cut down on power struggles in the home," she said.

With programs for 2-, 3- and 4-year-old children as well as a combined program for 3- and 4-year-olds, the school emphasizes woodworking, outdoor play, music, creative arts, field trips and presentations by such outsiders as police and firefighters for an educational program that also includes preschool math, language skills and science programs.

But Barker said the school "needs more children to survive" in its current form: with parents involved in the classrooms and a cost of $61.50 a month for a five-day morning program. Some private nursery schools that are not cooperatives range from $2,000 charge as much as $3,680 a year.

A move away from continual parent involvement "would change the nature of the school, especially the role of fathers here," said Francha Davis of Chevy Chase and president of the school. She pointed to the special talents of parents -- some musicians, one a photographer -- and said these persons added activities to school days that had enriched the program.

Parents' schedules now are set at the beginning of each year in a flexible manner to suit their needs. This is important because 90 percent of the mothers now have at least part-time jobs, Davis estimated.

Davis, whose job as president requires that she get every family involved in some aspect of school operations, said an open house is being planned for March to attract new families; of 10 families who attended an open house last year, eight enrolled their children.

There also are plans to start a summer school in 1983 that will not be a cooperative venture, in an effort to keep the school solvent. The nursery building also has been rented for weekend tumbling programs.