Northern Virginia jurisdictions will spend about $320,000 this spring to count their children, as part of a state-mandated triennial census.

The census of all children aged 1 to 19 years, and all handicapped children up to age 21, is required so that the state can determine how much money each school system should receive as its share of the proceeds from the one penny of every four in the state's sales tax that is reserved for education.

Local governments will receive $190 for every child they can claim, said Sam Cutchins, an assistant supervisor in the State Department of Education.

"Needless to say, we are assured they will be as thorough as they possibly can," Cutchins said. "I sometimes doubt there is a child in the state that won't be hunted down and counted."

The state pays local jurisdictions for all children counted, whether they attend public or private school, have dropped out or are in college. Some state officials say that the census can cost a jurisdiction as much as $200,000 to complete. Locally, Fairfax County will spend the most--$195,467--to conduct its census.

The census is the result of an old political deal worked out in the early 1960s, when the census law was passed, according to state officials.

At that time, many children in city and suburban areas were leaving public schools for private schools to avoid desegregation. State representatives from those areas, fearing that their constituents would lose sales tax money to rural areas where there were fewer private schools, demanded that their jurisdictions be allowed to count private school enrollments as well as those of public schools.

"There is no doubt the whole process would be easier and equitable if it were simply based on public school enrollments," said a state education official who asked not to be identified.

The schools have until June to finish the census, and must keep their records for three years in case the state decides to audit and make certain that each recorded child actually exists, Cutchins said.

Loudoun and Prince William counties are the only two in Northern Virginia sending out census takers. Other jurisdictions are conducting their census by mail.

Prince William County is paying 32 of its bus drivers the minimum wage to canvass door-to-door, and Loudoun pays residents 70 to 85 cents for each child they document. The census will cost Prince William $23,600 and Loudoun $23,000.

"I'm staggered by the thought of going from house to house," said Christine Smith, director of the census in Fairfax County. "We just have too many people to contemplate that."

The county already has mailed census forms to each residence and will mail out reminders next month to those who have not returned them.

Alexandria and Arlington County also are conducting the census by mail at a cost of $35,000 and $40,000, respectively.

"We sit back and wait for the returns to come in," said Joseph G. Guter, budget director for Arlington schools. "We get a good response since most of the residents realize it is to the county's benefit."

Perhaps nowhere in Northern Virginia is the census more important than in the small city of Falls Church, which has fewer than 1,000 school-age children.

There, officials have been carefully counting each child, first through a mailed census form and then with follow-up visits to each residence that does not reply.

"We are being extremely careful," said school official Bonnie Whiting.

So careful, in fact, that the city found one student who had falsified his address to attend a city school. He was charged back tuition and, Whiting jokes, as a result the city received more from him than the cost of the first census mailing.

"See, it's paying off already," she said.