Charter schools, once considered the experimental outliers of public education, are poised to go mainstream in Santa Clara County.

That’s due in part to sheer numbers. Eight new charter schools opened this school year, taking in 1,600 students. Last week alone, five charter schools were approved to open next August in the county. But perhaps more important, key places in the county have seen a transformation in attitude, from hostility and suspicion to acceptance and collaboration.

The growing number of charters cements the county’s reputation, along with the giant Los Angeles Unified district, as the most charter-friendly place in the state. In a month or so, the county school board will consider approving 20 more charters schools for Rocketship Education. The increase comes amid the widespread growth of charter schools in California. About 7 percent of the state’s public school children attend a charter, which are public schools operating independently from local school boards and most of the state Education Code.

This month, two charter school operators whose first schools were rejected several years ago won easy approval from local school boards. Both focus on educating poor and struggling students. Rocketship Education, whose initial charter application was rejected by the San Jose Unified School District in 2006, received unanimous approval from the district to open an elementary charter school next August. ACE Charter had to apply four times in 2006 and 2007 to get a middle school approved in East San Jose. But on one try, ACE won an OK from the East Side Union High School District to open a school, possibly in San Jose’s Mayfair district, next year.

“I’m very appreciative,” said Greg Lippman, executive director of ACE and co-founder of one of the first charter schools in the county, Downtown College Prep. “From the get-go, it was very clear the district was going to give us a thoughtful and fair review. They were really focused on the bottom line of student achievement.”

In many counties, charter applications are routinely denied, both by local school boards and upon appeal by the county school board. Five years ago, after its denial by San Jose Unified, Rocketship won approval from the Santa Clara County Board of Education for its flagship Rocketship Mateo Sheedy school. This time, the charter operator encountered an entirely different reception to its petition to open what will be its ninth elementary school in the county.

“A lot has happened in five years,” said San Jose Unified Assistant Superintendent Jason Willis. “Frankly, they have a track record of success with students we struggle to educate.” Rocketship’s speciality is low-income students who need a lot of support. Rocketship pointed to its high test scores. And, Willis said, the charter operator provided clearer specifics about its plans.

Rocketship’s policy manager, Evan Kohn, said, “We’re excited to put together this partnership.”

Changes on many sides transformed the reception for Rocketship and ACE. In San Jose Unified, there is a different superintendent, Vincent Matthews, who is a former charter school principal. Its teachers association did not oppose the charter proposal, as unions often do.

In East Side Union, Lippman called his proposal’s review “a really positive process.” In contrast, when he applied to open ACE Charter middle school, the Alum Rock Union School District turned him down three times, citing an insufficient budget, unsound curriculum and lack of parental support. After ACE won approval upon appeal to the county board of education, the school went on to post the highest gain in test scores — 127 points on the state’s 200-to-1,000 Academic Performance Index — of any school in the county in 2010.

Now with a changed administration and board in Alum Rock, ACE has collaborated with the district on building a $5.1 million permanent campus, aided with money from the San Jose Redevelopment Agency, on an undeveloped portion of Alum Rock’s Cesar Chavez Elementary campus.

“They’re allowing us to open a middle school three blocks from an existing middle school. That’s leadership from the staff, board of trustees and the principal at Chavez,” Lippman said. “They’ve been an incredibly good partner to ACE. In all areas, things are fundamentally different now in relations with Alum Rock.”

And the East Side Union staff recommended approving ACE’s high school, Superintendent Dan Moser said. While the district has OK’d six current charters, it hasn’t always approved all the applications that have been presented.

As designed under California law, charter schools put local school districts into a conundrum. When judging a charter application, districts may consider the quality of the proposed education program and the financial viability of the school operator, but cannot consider its own financial interests.

Yet the state creates a financial disincentive to approve charter applications. That’s because most school districts get state funding based on the number of children who attend, and lose money for every resident who enrolls in a charter. However, district costs don’t decrease commensurately with the loss in revenue.

With the County Office of Education working on a “charter compact” between public school and charter operators, officials hope that cooperation and sharing of strategies and practices will increase.

Both ACE and Rocketship believe they can share their successes with districts. “There are lessons to be learned,” Willis said, “in how to address student needs and in supporting their families.”

Contact Sharon Noguchi at 408-271-3775.