Prince George's County school officials and education activists say the county has miscalculated future school enrollments, which could lead to new housing near crowded schools and new schools outside neighborhoods where they are needed most.

"It looks like the numbers are skewed and that where we expect to see growth, it's not happening," said Donna Beck, an activist who has monitored county growth for several years. "We looked into those areas and found discrepancies in the information."

Nick Motta, chief of countywide planning, said his office this year used a new formula to calculate future enrollments at each of the 185 schools in the 130,000-student district and may need to adjust its findings. County officials will hold a public hearing today in Upper Marlboro on their school enrollment projections, which were finished last week.

"We have heard about a couple of things that show we need to reconsider what we have," Motta said. "It's not the easiest thing to project these kids."

The accuracy of enrollment projections is critical because county government leaders use the data when considering whether to grant building permits to developers. And school officials use the projections to determine where to build new schools, how to draw attendance boundaries and how much staff and resources to devote to each school.

As Prince George begins an unprecedented school construction campaign, with plans to build as many as 26 schools in the next decade, officials must have reliable numbers "to make sure development is dealt with in an equitable way," said county Board of Education member Kenneth E. Johnson (Mitchellville), who questioned the projections.

For example, he and others said they found it odd that enrollment at Kingsford Elementary in Mitchellville increased by 66 students last year, but the county estimated that just six new students will arrive at the school in the next five years.

"Having six new students compared to 66 last year does not make sense," Johnson said.

Nearby Ardmore Elementary has gained 104 students since 1994, though county planners projected enrollment would grow by three pupils in the next five years. And Brandywine Elementary's enrollment declined by 107 students in six years, but planners projected it would gain 240 students by 2004.

County planners said the school system's complicated busing patterns make it difficult to predict enrollments, noting that thousands of students are bused across Prince George's County because of a 26-year-old desegregation order and thousands more voluntarily attend magnet schools far from home. In addition, many families move into and out of the county each year.

This year, county planners asked school officials how many students they expected to advance to each grade in the next five years. Then they estimated the number of new students expected from new housing developments, deriving enrollment projections for each school.

County school officials also have had difficulties developing accurate enrollment estimates. For example, when Kingsford Elementary opened five years ago, it had dozens more students than its 800-student capacity, angering parents.

Three years ago, the county's park and planning division started developing its own school enrollment projections after county government leaders enacted legislation to control growth in areas with crowded schools. Under that measure, if enrollment at a school is projected to grow to more than 130 percent capacity, local development is halted for four years.

The measure has stalled at least one major housing development: Beech Tree, a proposed 2,400-unit subdivision near Upper Marlboro.

Del. James W. Hubbard (D-Prince George's) said he fears that the county's faulty enrollment projects are costing it revenue from developers, who must pay more to build in areas where schools are crowded.

Hubbard said he will introduce a bill that would grant permits to builders in Prince George's who are willing to pay a flat fee of $7,000 per housing unit to subsidize school construction. The county would no longer use enrollment projections to assess development impacts and fees.