The Prince George's County Council yesterday blocked the school board's plan to expand five high schools and instead pushed for building schools.

Council members said they agree with school officials that Prince George's faces a major problem -- a projected enrollment surge that could leave the county's high schools as many as 9,000 seats short by 2006. What emerged yesterday was a sharp disagreement over how to solve it.

In the next five years, school districts across the Washington region will feel the effects of a demographic phenomenon known as the "baby boom echo," as children born to baby boomers in the late 1980s and early 1990s reach high school age. To prepare, Prince George's educators in 2002 began to develop a strategy that focused on expanding several of the county's schools.

But the majority of County Council members voted against that approach yesterday, saying it is unwise to expand aging campuses.

"When you put new additions on an old house, you've got issues with the plumbing, you've got issues with electricity, you've got all sorts of issues that need to be contemplated," said council member Douglas J.J. Peters (D-Bowie).

County and school officials have agreed to build a high school in Upper Marlboro, large enough for 2,600 students when it opens in 2006, and to expand DuVal High School in Lanham. Over the school board's objections, however, the council voted yesterday to spend the next few months studying whether to build another high school instead of expanding five schools.

In the meantime, the county will keep $4.9 million on reserve for fiscal 2005 to use on whichever option the council selects.

The council's action, which came in the form of a committee vote, angered Prince George's schools chief Andre J. Hornsby, who said the issue has been studied enough. Unless construction begins to expand high schools this summer, he said, they will not be ready in time for the increase in students.

"The council has now assumed responsibility for providing space for children in the year 2006," Hornsby told reporters after the meeting.

There are other consequences to the council's decision, school officials said. Currently, thousands of Prince George's high school students are housed in 198 temporary classrooms. Without the proposed school expansions -- and the 3,000-plus seats they would add -- the district would need about 150 temporary classrooms on campuses that aren't large enough to accommodate them, school officials said. High Point High School in Beltsville, for example, would require 30 more trailers, but the campus can hold only 10, they said.

The school system also stands to lose millions of dollars that have been spent on designing the expansions, according to Hornsby. The County Council agreed last year to let the school system spend $3.5 million on the planning phase of the projects.

"Some of that is going to have to be the burden of the decision that happened [yesterday]," said school board Chairman Beatrice P. Tignor (Upper Marlboro).

Council member Peter A. Shapiro (D-Brentwood) said that the council would prefer to lose that money than to make a bad decision. Expanding high schools "doesn't feel like it's a long-term solution," he said. "In the long run, we're going to need the capacity. Why not give the students the highest-quality facility?"

The highest-quality facility, Shapiro and other council members argued, is not a high school with more than 2,400 students. Much of yesterday's discussion centered on a philosophical divide between Hornsby and the council over the size of high schools.

"There's no problem with 2,400 [or] 2,500 children in a school," Hornsby said, noting that the county's top three high schools have more than 2,500 students.

"People get confused about size," he said. "Size is not the variable. The variable is the leadership of the schools and the quality of the instruction."

Tempers flared during the meeting. Immediately after the vote, Hornsby walked out of the council chambers, taking several of his deputies with him, as one council member was mid-sentence. A spokeswoman for Hornsby later said he was rushing to catch a flight.