Student improvement on standardized tests has heartened officials at D.C.'s charter schools, but expansion efforts are more focused on bolstering quality than increasing enrollment.

At the middle and high school levels, the percentage of charter students scoring at least "proficient" on the city's reading test jumped more 6 six points compared with last year, to about 53 percent. Math proficiency in secondary schools saw more progress, jumping 9 points to nearly 57 percent.

At the elementary level, gains were smaller. Both reading and math scores improved less than 1 percent over 2007-2008, compared with a 4-point reading gain and an 8-point math gain in traditional D.C. schools.

"News at the elementary level for charters didn't look great at first blush," said Mike Petrilli, vice president at the pro-charter Thomas B. Fordham Institute. "But at schools that have been around awhile and where we can see growth over time, things look better."

The city's 58 charter schools serve about 26,000 students, more than one-third of the District's total.

Having attracted enough students to earn their place on the city's educational landscape, members of the D.C. Public Charter School Board said they have been able to step back and focus on quality. The group skipped a new school application process during the past year to instead create a new framework for measuring existing schools' success.

"Expanding the number of charters is not as important right now as quality and capacity," said Josephine Baker, executive director of the board.

Board Chairman Tom Nida said coming tough budget years likely would require public charters and the regular school system to work more closely to expand quality and capacity with limited funds.

"I don't think we'll see significant growth in the number of new charters going ahead, but the organic growth of successful, existing charters looking to add grade levels or expand to different campuses," Nida said.

The truest measure of the movement's success will come when enrollment in city schools, both charters and traditional, begins to creep back up, Nida said. Throughout the 1960s, nearly 150,000 students attended city public schools. Today, enrollment is barely above 70,000. If that turns around, advocates said, it will be evidence that charters have helped raise the bar at traditional schools.

"I don't see any reason to believe charters won't continue to expand in the District," Petrilli said. "There still seems to be demand. When new schools open, parents flock to them."