The number of children in the District’s child welfare system is continuing to drop, prompting officials to take a fresh look at how the city spends its $265 million child welfare budget.

Across the region and the country, social service agencies are seeing such declines, although the implications are especially significant for the District, which has a long history of child welfare crises.

No single factor explains the drop in the District, but experts believe that the city’s changing demographics and renewed emphasis on keeping troubled families together are driving the trend.

According to the D.C. Child and Family Services Agency, the number of children it supervises has fallen to 3,400 from 4,654 in early 2009, a change of almost 30 percent.

Just over half of the 3,400 are in foster care, and the rest are living with their families. The numbers of children in foster care and under home supervision have decreased, according to the CFSA.

With child welfare officials due to appear Wednesday before the D.C. Council for a budget hearing, the agency has been facing questions about whether it can make do with less money and what effect a reduced budget would have on its performance.

They are vital questions for an agency that has long been one of the city’s most troubled and most scrutinized. For more than two decades, the CFSA has been monitored by a federal judge as part of a class-action lawsuit, known as LaShawn v. Gray.

In recent years, the city has sought to end the lawsuit, saying that the agency has corrected the most serious shortcomings. But continuing problems have clouded the progress the agency has made.

Most dramatically, Banita Jacks was convicted in 2009 of murdering her four daughters, who had been left with Jacks despite concerns that the children might be in danger. Less prominently, the agency has struggled to place older foster children in permanent homes.

But even if CFSA’s caseloads are getting lighter, a shrinking budget could hinder the agency’s halting progress, its top official said.

“If you don’t need to spend a dollar, there should be a decline,” Brenda Donald, recently appointed by Mayor Vincent C. Gray (D) for a second tour as CFSA director, said in an interview. But the decline in the number of children in foster care, for example, doesn’t mean the CFSA should be fiscally starved. “You want to reinvest some of those dollars used for placement into family preservation. It’s not a one-to-one reduction.”

Indeed, the CFSA budgets have not shrunk as quickly as the number of children it serves. In 2009, the CFSA spent about $289 million. For fiscal 2013, the proposed budget is $257 million. That is a decrease of about 10 percent, much less than the drop in the number of children under the agency’s supervision over the same period.

Council member Jim Graham (D-Ward 1), chairman of the Committee on Human Services, which oversees the CFSA, has been skeptical of the agency’s stated budget needs.

“We need to make sure that we manage resources at CFSA better,” Graham tweeted this month. A subsequent tweet echoed his doubts: “CFSA has seen a decline in its caseload, but the staffing levels have remained the same. My question is why?”

In an interview, Graham reiterated his concerns. “If this caseload continues to decline as dramatically as it appears to be declining, that means that the money we’re spending . . . is really called into question,” he said. “If they’re not showing surpluses, I wonder about how real the decline is. You can’t have it both ways.”

Donald has tried to head off such concerns. At a budget briefing last month for providers who work with the agency, she spoke of “right-sizing” — getting the CFSA’s budget in line with needs. When some raised questions about proposed cuts, including a $12 million decrease in “prevention services,” Donald said that funding changes won’t compromise the CFSA’s “core services.”

Because foster care is expensive, Donald said, she wants to focus on keeping children with their families. Her focus on in-home care mirrors a national trend: The U.S. foster care population fell about 21 percent between 2003 and 2010 and, according to a 2010 report from the Metropolitan Washington Council of Governments, the number of children in foster care across the region fell about 10 percent between 2008 and 2010.

“We only want to bring kids into foster care that need to be in foster care for their safety,” Donald said in an interview, adding that “the days of kids being raised in the foster-care system are hopefully over.”

“She makes a convincing case that she can make placements at a lower cost that what we’ve seen,” Graham said. “I want to believe in that.”

Not everyone agrees. “I am willing to accept the new Director’s view that they can do what is needed with a flat budget but I would not support additional cuts this year,” Judith Meltzer, the federal court-appointed CFSA monitor, said in an e-mail.

Meltzer, who is deputy director of the Center for the Study of Social Policy, said Donald’s budget must be preserved so that it can address at-risk children’s needs beyond foster care, including investigations of abuse. “I would not decrease the amount of available funding,” she wrote.

But it might be hard to defend a budget for the District’s shrinking foster-care population. Olivia Golden, head of child welfare in the District from 2001 to 2004, thinks that the decrease in foster kids means that the agency is doing a good job.

“The District made big improvements in the years I was there,” she said. “D.C. had not had a lot of success in having children move to adoption. We worked closely with family court and . . . I think the District has sustained those improvements.”

Demographic changes also play a role, including a decrease in the number of children in the District. Data from the 2010 census show that the city had 14,000 fewer children than in 2000.

“It’s part of the bigger economic and demographic changes happening in D.C.,” said Peter Tatian of the Urban Institute.

Children are 17 percent of the District’s population, compared with 20 percent a decade ago. But significantly for the CFSA, many of the neighborhoods that have seen drops in the number of children are east of the Anacostia River. Many of those communities are poor, and they have long been disproportionately represented in the city’s child welfare system.

Graham remains cautious. “We’re still left with huge problems associated with foster care,” he said. “I want to make sure that, whatever the caseload, that it’s not a pipeline to chronic unemployment, poverty and substance abuse.”

Donald, who noted that she has been on the job for only three months, said she is fighting to avoid cuts. “I don’t think it’s about more money,” she said. “It’s about better strategy and greater accountability.”