One of Atlanta’s first and most successful charter schools wants to expand into high school grades, but it lacks the support of an important backer: Superintendent Erroll Davis.

Davis is expected to recommend denial of Drew Charter’s plan to add more elementary students and build a new high school. Drew supporters say their program’s high-performing alumni are slipping through the cracks when they enter traditional high schools.

Atlanta school board members get the final say at tonight’s school board meeting.

The objection to Drew’s expansion is notable for Atlanta Public Schools, a district more friendly than most to charter schools. But it echoes the conflict in districts across metro Atlanta, where the ambitions of charter schools are almost always at odds with traditional public schools.

The main reason? Money.

Charter schools are public schools; they’re free to students and run independently of local school boards, although they must follow state guidelines. State tax dollars follow a student from traditional schools to the charter of choice, meaning traditional schools lose money as they lose enrollment.

APS sends about 8 percent of its budget to charter schools. Enrollment in Atlanta charter schools is projected to increase next year, according to district budget documents.

Davis said Atlanta isn’t opposed to adding more charters, but says his system has too many empty seats to support a new high school. The existing Jackson High, about three miles from the proposed Drew site, expects about 876 students next year although it has space for 1,450. All told, APS has 6,200 empty seats at the high school level.

Drew’s proposed high school won’t offer anything students can’t get at a traditional high school, Davis added.

“If I were to come before the board and say ‘I’d like to build another high school,’ I’d be laughed out of the building because one of the things we made clear in the redistricting is that we have too many high schools,” he said. “The only reason I would agree to an additional high school is if it were strategically meeting a need we weren’t. And I have yet to see that.”

Drew supporters say they have built a successful program in early and middle grades and want to continue the success with a $55 million high school. Plans are to open the 200,000-square foot high school in 2013-14 with 100 freshmen and add one class per year until the school reaches 600 students in 2023.

The money will be raised by the East Lake Foundation, Drew’s primary nonprofit supporter.

“We feel like our kids are on a trajectory, if they could just continue the kind of culture, intensity and academic design we’ve started here, they would be on a path to college, success and life,” said Cynthia Kuhlman, chairwoman of the board of Drew Charter School Inc.

It’s been a rocky few years for Georgia charter schools. In 2011, a state Supreme Court ruling reduced the number of ways charters can win approval if denied by the local school board. That ruling came after Gwinnett and other districts filed a lawsuit arguing the Georgia Charter Schools Commission, created by the Legislature in 2008 to approve charters, was taking local tax dollars away from school districts at a time many face budget cuts.

This fall, voters will decide on a constitutional amendment to essentially reverse that ruling and give the state more control to override local school boards.

Atlanta has 12 independent charter schools, more than any other district in the state. But denials are not unusual: The charter school approval rate is 20 percent to 25 percent, in line with the national average, according to APS officials. The district has denied 23 charters and approved seven in the past three years.

By contrast, Gwinnett County Public Schools, the state’s largest system with about 160,000 students, has one independent charter school.

Davis says the Drew expansion would not only add unneeded high school seats, but also conflict with plans to improve schools in southeast Atlanta, where several charters already exist. As part of a massive redistricting approved in April, the board agreed to close seven schools and eliminate some of the district’s 13,000 empty seats. Plans were approved to make $40 million in improvements at Jackson High, including the addition of an International Baccalaureate program.

“I am not going to say whether I believe Drew can or cannot produce a good high school. All I know is we can, and we can in this same area,” Davis said.

Drew opened 12 years ago as Atlanta’s first charter. About 1,110 students are enrolled in the school’s birth through eighth-grade program, a holistic education approach that’s helped revitalize Atlanta’s once-derelict East Lake neighborhood. State data show the school has more black and low-income students meeting or exceeding state standards than any other school in the district.

Drew has influential backers such as former Mayor Shirley Franklin and developer Tom Cousins, a founder. Its pre-kindergarten program receives support from the Cox Foundation. Cox Enterprises is an Atlanta-based communications, auto services and media company whose holdings include The Atlanta Journal-Constitution.

It’s unclear how much Davis’ opposition will influence the school board. Four members reached Friday declined to say how they’d vote; others didn’t immediately respond.

Atlanta parent Ellen Buettner, whose children attend Toomer Elementary and will eventually go to Jackson High, said she believes there is room on the east side for two high-performing high schools.

“Although I am heavily invested in Toomer and will turn my sights on Jackson soon, I don’t think limiting parent options is the way to go,” she said.

Louis Erste, director of the charter school division at the Georgia Department of Education, said state law is clear that districts should approve charter applications that meet state rules and guidelines. School boards shouldn’t deny an application for fear it will hurt efforts to revitalize a nearby school, but they could deny a charter if they have concerns about low enrollment, he said.

Drew supporters aren’t deterred so far.

“We’re gathering some great community support. We have not faced the possibility of a negative vote,” Kuhlman said. “We want to be an Atlanta Public Schools charter. Our kids live in the city, and it is important for us to be in Atlanta Public Schools.”