Roman Catholic high schools in Washington will end coeducation and consolidate six schools into four -- two for girls and two for boys -- under a school reorganization plan announced this week by Archbishop James A. Hickey.

Church officials say the reorganization is needed to make the most efficient use of resources and to improve the quality and availability of Catholic education for girls. The changes, scheduled to take at least three years to complete, are expected to affect some 850 students and to cost $4.5 million.

The plan calls for the elimination of two girls' schools--St. Cecilia's at 601 East Capitol St. and Immaculate Conception at 950 24th St NW.

Coeducation at St. Anthony's High School at 1001 Lawrence St. NE will end, and the school will expand to accommodate 400 girls and will change its name to All Saints. The 60 boys presently enrolled will transfer either to Mackin, at 2200 California St. NW, or to Archbishop Carroll at 4300 Harewood Rd. Both of those schools will continue as schools for boys only.

St. Patrick's Academy, a girls' school at 924 G St. NW, is to be remodeled and expanded.

Catholic schools in the city that are not operated by the archdiocese will not be affected by the planned changes.

The reorganization blueprint announced this week is the fourth effort by church officials since 1968 to reapportion the church's educational resources in the District for their most effective use in light of two massive demographic trends: the post-World War II movement to the suburbs and the mass exodus from Catholic schools in the '60s.

Four years ago, a plan to consolidate St. Cecilia, Immaculate Conception and St. Patrick's into a super-school at St. Anthony's drew so much opposition that it was eventually shelved.

Leonard DeFiore, archdiocesan school superintendent, said the present plan is an improvement over earlier proposals.

DeFiore said that with the exception of St. Cecilia's, all the schools involved in the restructuring are in need of repair. "They've all been scotch-taped together in hopes they would survive until we move to the new plan," he said.

Unlike elementary schools, which are usually tied to a neighborhood parish, parochial high schools draw their students from a wider area. "Kids crisscross all kinds of crazy patterns" in selecting a high school, DeFiore said. At Immaculate Conception in Foggy Bottom, for example, "the majority come from the Southeast. There's even a bus from Bolling Air Force Base," he said.

DeFiore said approximately 2,000 parochial elementary and high school students travel from Maryland to schools in the city -- many dropped off by parents on their way to work -- with 1,000 going the other way. He said enrollment in D.C.'s Catholic high schools has been "remarkably stable" for the past ten years.

DeFiore said the end of coeducation in archdiocesan high schools was "certainly a loss." But noting that there are currently only 65 boys among St. Anthony's 192 students, he said "the demand for coeducation is not overwhelming."