In April they began pestering their mother for details on when, where and how long it would be. That elusive day, June 22, couldn't get here quick enough for the seven Roberts children of Alexandria. To them there's only one thing more fun than summer vacation: vacation Bible school.

Next week the baseball bat- and Bible-toting Roberts children will finally get their wish and start their beloved Bible school, as will thousands of other Washington-area children enrolled in free church-run programs offering recreation, crafts, singing and religious study.

The programs, which are run for youngsters between the ages of 4 and 18 but focus primarily on grade school and junior high school students, have become as much a Washington-area summer ritual as the heat and tourists because they're as popular with parents as they are with the children.

The majority of the offerings begin Monday, generally running anywhere from one to six weeks, with others opening during the course of the summer, and in the process "they take children off the streets during those hours" and "give the parents some free time to work or relax and take some of the burden off the recreation parks and playgrounds," said the Rev. Ernest Gibson, director of the Council of Churches of Greater Washington.

To Cherie Roberts, 13, the best part of vacation Bible school is kickball. Cherie, starting her eighth year with the program, thinks the experience has not only honed her kickball game but her reading. Her sister, Felicia, 11, enjoys playing Bible games most.

Their mother, Naomi Roberts, is pleased with the school held at Mount Vernon Baptist Association, even though her family is not Baptist. "I like it because it makes them happy," she said. "They have learned all about love and sharing and getting along with other children."

"And, oh boy, do they look forward to it," said Roberts, whose nine children have all participated in the program at some point in the last 10 years. "It seems like they would rather do that [attend Bible school] than go any place. When that van pulls up out front, all you hear are doors slamming and kids running from everywhere."

Summer programs like Mount Jezreel's, which include intensive study of scripture, Bible games and prayer as well as recreation, are generally the domain of the Southern Baptists although some other Protestant churches such as the Methodists, Presbyterians, and Episcopalians have opened similar schools in the past few decades. The Catholics run some programs as well.

Nobody knows exactly how many children are enrolled in the programs because many denominations do not keep records. The Southern Baptists do, however, and they report a steady rise in attendance, with enrollment expected to hit nearly 17,000 in this area. The Southern Baptists, who look upon the programs as a major recruiting and teaching tool, reported a nationwide record attendance last year of well over 3 million.

Other denominations report little or no growth or a decline in attendance, largely because the number of school-age children in the population has fallen. Some programs are also facing some difficulties because of budget cutbacks.

For example, the director of the major summer recreation program sponsored by the Catholic archdiocese here said government budget cuts and fewer volunteers (because there are more working mothers) will force him to do without tutors and decrease the eight-week program to six weeks.

Besides sports, the 100 children taking part in the program at St. Martin's Church take field trips to black historical sites and arts and crafts classes. No religion is taught, according to the Rev. Robert Guillen, program director. The program, for children of grade school and junior high age, begins June 29.

National City Christian Church, which has run a highly successful "summer enrichment program" for disadvantaged children for the last few years, is facing enrollment difficulty this year. Fewer than 25 children in grades 3 to 5 have registered for the free six-week program of academic study, recreation and lunch beginning Monday.

"We've had dozens of inquiries from middle-class parents of children who are willing to pay to send their kids here," said Artye Hellner, director of the program, which in the past has typically enrolled about 50 children a summer. "But we designed it for poorer children and want to keep it that way if possible."

"We know the children are interested," said Hellner, "because when we send our volunteers to the schools they all say they want to come. But the problem is getting their parents to register them." Hellner said most children are enrolled through schools, and in the past parents were nudged by church volunteers who went from door to door, reminding them of the program and collecting registration slips. This year, the workers are not as familiar or as well-known in the poorer black neighborhoods and that is why enrollment has slipped, Hellner said.

Declining enrollment has caused other churches to condense or completely do away with their traditional week-long summer church schools. "We found that we could never settle on a week that was convenient for everyone, and to be honest, we just don't have the number of kids we used to have," said the Rev. William Bond, associate pastor of Twinbrook Baptist Church in Rockville.

So recently, Twinbrook held a weekend Bible school and doubled attendance over last year's week-long school because people weren't out of town on vacation, and planners devised an attractive program.

Besides Bible schools, individual churches sponsor summer-long tutoring programs, week-long children's camps and music camps. Many churches have churchwide summer activities including softball teams, retreats, picnics and camping trips.

Formal church-related summer programs took root 83 years ago when a Southern Baptist woman leased a beer garden on New York's East Side and spent summer weeks teaching Bible classes to immigrant children, according to the Rev. Arthur Burcham, a vacation Bible school consultant with the Southern Baptists.

It was successful and the idea caught on. Soon the Presbyterian Church in the U.S.A. instituted a national program, but the Baptists caught up again in the 1920s and remain pre-eminent in the field today.

Now typical Baptist summer fare consists of three options -- a 10-day church school for children enrolled in Sunday school, vacation Bible school and back yard Bible clubs for several days a summer.

Besides recreation, the schools provide converts, according to Burcham, who said, "Probably one-fourth of all children and youth who join the Baptist Church do so as a result of vacation Bible school."