The number of D.C. public charter schools will grow from 42 to as many as 61 over the next year, making a shortage of affordable buildings even more acute, according to charter school advocates.

Over the past few years, the District's real estate boom has heightened competition for space among the independently run schools, pushing up prices and putting many properties out of reach. With 11 charter schools opening this fall and eight having won initial approval to open in fall 2006, charter advocates say city officials must quickly come up with a solution to the space problem.

About 15,000 students attend charter schools, a figure expected to grow by at least 1,000 this fall. The traditional public school system has about 62,000 students, and enrollment has declined steadily.

"We're seeing a spike in charter school applications and approvals, and we're seeing more [existing] schools adding campuses and expanding," said Robert Cane, executive director of Friends of Choice in Urban Schools, a charter school advocacy organization. The space crunch, he said, "will worsen dramatically unless we can get public space in [D.C. public school] buildings not being used or surplus schools under the control of the mayor."

Pressed by members of the D.C. Council and Congress to address the problem, the D.C. Board of Education approved a plan in April to allow charter schools to co-locate in 10 underused traditional public school buildings. School Superintendent Clifford B. Janey has said he plans to complete a master facilities plan in December, and charter officials are hoping that his study will result in more school system buildings becoming available.

Several of the charter schools opening in the fall have had to scramble to find temporary quarters, and at least one -- the Academy for Learning Through the Arts -- is still looking for a site.

Officials at the academy began that search in February, as soon as their application to open the school was approved by the D.C. Public Charter School Board. Early this month, they thought they had found rental space in an office building on F Street NW. But the agreement fell through last week, said academy founder and chief executive Patricia Mitchell.

The academy was conceived as a cutting-edge school for 156 students in kindergarten through sixth grade. But despite initial strong interest from parents and teachers, Mitchell said many of them will not sign on because the school's site is up in the air. With just 10 weeks to go until classes start, the school has enrolled only about 55 students.

School officials have conducted numerous interviews to fill about 14 teaching positions but have yet to extend any contract offers. Last week, two teachers who had been wooed for months took jobs with more certainty.

"We want to hire the best teachers in July, so they can work on the curriculum. But you can't do that without a site," said Mitchell, who served as director of Fillmore Arts Center, which offers art and music classes to students at six D.C. public schools, and is taking a leave of absence next month. "You have to pause and take a breath when the building falls through and two teachers say they can't wait for us to get a building."

Hope Community Public Charter School, also scheduled to begin classes in the fall, found space in an Upper Northwest church that had been vacated by a charter school this year -- but it had to overcome some fierce competition.

"They had six charter schools initially [vying for the space], and that number was whittled down to four," said George Sanker, principal of Hope Community. Church officials finally selected his school after extensive interviewing, Sanker said.

The school board has scheduled a hearing Wednesday to discuss lease applications it has received from charter schools at 10 underused buildings in the regular public school system. At most of the buildings, two or more charter schools are competing for the space.

Robin R.A. O'Hara, planning manager for the school system's office of facilities management, said the board will decide on the leases based on a charter school's compatibility with the traditional school whose facility it would use, as well as the charter school's ability to provide capital improvements to the building. Charter schools receive a facilities allowance from the city, which some supplement with private fundraising.

"The hope is that if a charter school co-locates, capital improvements can be made to benefit all the students in the building," O'Hara said.

Charter school advocates say the co-location program is far from perfect. The school board is not expected to sign the leases until July, giving the schools less than two months to renovate the buildings. The leases are for only a year, offering the charter schools little long-term stability. And depending on the agreement worked out with the school system, a charter school might not be able to use its building's cafeteria, library, playground and parking lot.

Moreover, the school system has not determined how much it will charge the schools, advocates say.

"The lateness of the hour isn't just bad for charter schools; it's bad for the process," Cane said.

Meanwhile, organizers of the Academy for Learning Through the Arts are hedging their bets. They have put in applications at two of the public schools on the co-location list and last week toured another possible site, a community center in Northwest.

"I cannot risk that we will not have a school building in September," Mitchell said. "It is my most important mission."

Patricia Mitchell is looking for space for her charter school.