PLEASANT HILL -- The new Clayton Valley Charter High School is such a hit that the campus is bursting at the seams. But it appears that as many as150 students on a waiting list may be able to attend classes on the Cal State East Bay Concord campus this fall.

The Contra Costa County Board of Education voted 4-1 on Wednesday to allow Clayton Valley to begin negotiations with the college about leasing space for the charter school on the nearby campus.

Trustee Daniel Gomes voted against the proposal after raising concerns that more students at the charter might financially harm the Mt. Diablo school district. The district must pay the charter more money per student than it receives from the state, which it says costs at least $1.7 million a year.

Trustee Pamela Mirabella also raised questions about the cost to the district but admitted that the debate over the net loss or gain is unresolved. The County Office of Education has prepared an analysis of cost impacts to the district from the charter and says the district would break even if it reduced central office staff because of declining enrollment.

County board President Richard Asadoorian and trustees Ellen Elster and Cynthia Ruehlig enthusiastically supported the expansion proposal, which includes an Early College Academy to be located on the nearby college campus.

Ruehlig said the proposal highlights the freedom that charter schools have to be innovative. "It makes it worth the controversy and the drama that surrounds the existence of Clayton Valley Charter High School," Ruehlig said. "My only hope is that you do not grow too big that you lose the small community feel -- that you continue to be in touch with parents, students and teachers."

Dave Linzey, executive director of the charter, said the new academy would complement three existing academies that provide small learning communities.

"We don't want to lose that," he said. "We want to create more of that, trying to build our current academies with more kids in those 'schools within schools,' in a sense."

Theresa Harrington covers education. Reach her at 925-945-4764. Follow her at Twitter.com/tunedtotoheresa.