Howard County School Superintendent Sydney L. Cousin has unveiled what he called a "prudent and conservative" redistricting plan that leaves three high schools untouched even as it shifts hundreds of other students to fill the county's newest school.

The plan, presented to the Board of Education last week, would draw students from Centennial, Glenelg, Mount Hebron and River Hill high schools to make up the enrollment of Marriott's Ridge High School in Marriottsville. The school is scheduled to open in August with freshmen and sophomores.

The reassignment of students to Marriott's Ridge creates hundreds of empty seats at the county's western and northern high schools that must in turn be filled. The result will be a ripple of changes across the county. Cousin said the redistricting is designed not only to fill Marriott's Ridge but also to balance enrollments throughout the county and provide relief to crowded schools.

In fast-growing Howard, redistricting has become a fact of life. David Drown, director of the schools' geographic systems, said about 700 new students are enrolling in the county's public schools each year -- roughly enough to fill a middle school. For a handful of unlucky students, boundary line changes this year could mean switching schools for the fourth time in as many years.

Cousin said he hopes this year's plan will be the last major redistricting for several years. To that end, some schools were left slightly above or below their target enrollments because officials predicted significant changes in their population over the next few years. Cousin's proposal, which closely follows the "green plan" devised by the school boundary line committee, would not affect Wilde Lake, Reservoir and Atholton high schools. The committee also had come up with a "red plan" that would have had some impact on every high school in the county.

"My goal tonight is to make everyone happy," Cousin told a crowd of parents during last week's board meeting.

Under his plan, most of the students at Marriott's Ridge would come from Mount Hebron's western district, with roughly 300 total students affected. Without redistricting, the school would be at 137 percent of capacity. Still, some parents said too many students would be affected by the change.

"All along we've expressed concerns about the number of students that are being moved," said Cindy Ardinger, president of Mount Hebron's PTA.

An additional 54 students from Centennial, mostly from its northwestern district, would also move. River Hill would lose about 70 students from the northern part of its district. And about 140 students who live in the Mount View Middle School district and attend Glenelg would be moved to the new high school.

Mount Hebron would receive about 100 students under the plan from the Worthington and Ellicott City neighborhoods currently in Centennial's district. Centennial, in turn, would get about 45 students from crowded Howard High School who live in the Wheatfield neighborhood. And Glenelg would draw 77 River Hill students living in the Green Bridge area.

Meanwhile, Howard High would also send about 45 students from the Brightfield and Montgomery Run neighborhoods to Long Reach High School. That would bring the school down to 104 percent of capacity, from a high of 119 percent without redistricting.

Oakland Mills High School suffers from the opposite problem: It has too few students. Cousin's plan would send about 130 students from Hammond High School's northeastern district to Oakland Mills.

Drown said the plan does not include any alterations to Reservoir's boundary lines because of the anticipated influx of students from the new Maple Lawn Farms development in Fulton. River Hill has also been left more open in case Reservoir becomes crowded and students must be moved out.

Several smaller changes have been made to middle school boundary lines as well. The most significant is a shift of 33 students from Patapsco Middle School to Burleigh Manor Middle School.

Cousin said he relied heavily on the plan drafted by the citizens school boundary line committee to develop his proposal.

"It wasn't me or the staff starting from scratch," he said.

The school board will hold a public work session on the boundary lines changes this evening at 7:30 at the Board of Education, 10910 Route 108, Ellicott City, and again at the same time Nov. 16. Public hearings are scheduled for the same time and place Tuesday and Nov. 18. The board is scheduled to vote on the redistricting plan Nov. 23.

Superintendent Sydney L. Cousin called his plan "conservative."