The D.C. public schools this fall are opening all-day prekindergarten classes in 40 elementary schools across the city to teach 3- and 4-year-olds to read, write and count.

About 600 students will be enrolled in the $1.1 million program that was initiated because of the growing number of single working mothers and students' increased achievement with a head start on their education.

"So many of our parents are single working women who don't have many other resources for their children during the day," said Constance Mair, coordinator for the prekindergarten program. "If they know their child is in school learning, then these parents can pursue their goals without the worry . . . . This is a way the schools can help support the parents," she said.

Handicapped children are enrolled in a separate all-day prekindergarten program.

Previously District public schools offered only half-day prekindergarten classes. The District is the only local jurisdiction offering the all-day classes, which are provided at no cost to parents.

"The research continues to show us that children who attend preschool generally perform better than those without," said associate superintendent James T. Guines. "For every 4-year-old that spends a full day learning in a healthy environment it will lessen the chance for one more dropout or teen-age pregnancy when they reach 16," he said.

Parents who wanted to enroll their children in the new classes had to sign up last spring and some parents, unaware of the new program, missed the deadline and were disappointed when they inquired about it last week.

One of those was Veronica Stewart, 26, whose 3-year-old daughter now attends half-day pre-kindergarten. "Of course I prefer all day for my daughter, because I work and I can't get off at lunch to pick her up. If they're going to have all day then they should have it for all the kids."

Some of the all-day programs have opened and all are scheduled to be in operation by Oct. 1, according to school officials.

The program is under way at Rudolph Elementary School at Second and Hamilton streets NW, to the delight of Ethel Price, whose 4-year-old granddaughter is among the students.

"I think it's just great, kids are so much smarter these days," Price said as she dropped off her granddaughter last week. "They ask so many questions and they can get answers here. If she was home she would be just running around the house burning up energy."

Camille Locke, 28, whose daughter Makea, 4, attends the same program said, "I think being in a constructive environment all day will prepare her much better for kindergarten. All homes are not good homes to learn and our kids -- and I mean black children -- need all the extra learning they can get."

The children's teacher, Martha Conley, has a lot in common with her pupils.

"This is my first experience teaching all day and this is their first experience learning all day," Conley said. "Just look at their faces," she said, pointing to the 14 children sitting in miniature wooden chairs at their desks. "This is going to work out just fine."

She added, "I plan to have these children writing their names in a couple of months and they'll learn to recognize pictures and associate them with words and they'll learn phonics and we'll go on trips . . . . We need a whole day to do all the things I have planned," she said.

These are the elementary schools that have all-day prekindergarten classes: Northeast: Wilson, Webb, Emery, Wheatley, Young, Langdon, Blow, Thomas, Richardson, Winston, Drew. Northwest: Montgomery, Oyster, Hyde, Rudolph, Brightwood, Raymond, Eaton, Meyer, Cooke, Bruce-Monroe, Adams. Southeast: Turner, Hendley, Washington Highlands, Birney, Malcolm X, McGogney, Stanton, Ketcham, Tyler, Giddings, Orr, Nalle, Plummer, Weatherless. Southwest: Syphax, Bowen and Bancroft.