Charles County's elected leaders yesterday slashed the number of houses that may be built in the rapidly growing jurisdiction, saying they are determined not to let students from new homes overwhelm public schools.

The action restricts home building near crowded schools. Because many schools in the Southern Maryland county already are over capacity, this could cut the pace of home building in half for at least the next six months.

The controls rank among the most stringent yet placed on the residential growth that has spread across Washington's suburbs, bringing traffic jams and crowded classrooms to once-sleepy communities.

A backlash has been growing. In the past two years, candidates advocating slower growth have won elections in nearly all of the area's outer suburbs, as well as Fairfax County and Montgomery County at the region's core.

Last week, Loudoun County's new slow-growth board reserved funds to battle anticipated legal challenges as it seeks to rein in development. Last month, Howard County proposed rules to more tightly tie home building to school capacity--the same strategy followed yesterday in Charles County.

Charles officials called their action the most far-reaching to be enacted in Maryland. Building industry officials agreed.

"It's going to have a devastating effect," said Vic Valentine, assistant director of government affairs for the Maryland-National Capital Building Industry Association, a trade group.

"No other jurisdiction has attacked the problem with this ferocity," said county Board of Commissioners President Murray D. Levy (D-At Large), who is active in the statewide organization of Maryland county officials.

By a 4 to 0 vote with one of its members absent, the Board of Commissioners determined that during the first half of this year, county planners should aim to allow just 251 more dwelling units.

Most of those--188 of the total--would be new housing units in developments that will be allowed to move on to final stages of approval. The remaining 63 could come from projects that were on the verge of final county approval last July, when commissioners decided to tightly link construction approval to school capacity.

Such builders are guaranteed to receive building permits if they wish. They claimed roughly 300 permits from July through November last year, and it is unclear how many they might seek over the next six months.

Under the new policy, officials scrutinize the number of empty seats in the county's public schools and decide how many additional pupils can be accommodated. They then use a formula to calculate the number of homes that would have that number of children and set the level of construction approvals accordingly.

The figure selected yesterday would, on an annual pace, produce 502 building permits--or 44 percent of the number granted last year, when the county issued permits for 1,154 dwelling units.

The stricture is expected to ease, perhaps as early as this July, after the county gains a state commitment to help fund a new high school. The high school's seats then could be included in school capacity calculations.

But officials said the policy will continue to dampen housing growth in the county, where the population has grown to roughly 124,000 people--an increase of 23 percent in the past 10 years.

Since 1990, public school attendance has increased by roughly 2,500 students, or enough for nearly four elementary schools, reaching 21,729 pupils in September.

The growth coincided with lagging scores on standardized tests. Last year, commissioners raised taxes to help pay for programs aimed at heightened academic achievement in the county's 31 schools. "If they are perpetually, chronically overcrowded, it's going to have an impact," said Levy, the commissioner.

County leaders call school improvement one of several steps needed to reverse disturbing trends that surfaced in the mid-1990s. These include sagging property values, a heightened crime rate and a relative lack of good-paying jobs.

"Is there anybody out there that thinks growth has been going well?" Levy said. "We're trying. We're doing something. . . . We can change the pattern and the quantity and the quality of growth in Charles County."