D.C. Mayor Muriel E. Bowser (D) announced Monday that her deputy mayor for health and human services Brenda Donald, right, will return to her old job leading the District's child welfare agency. (Fenit Nirappil/TWP)

Mayor Muriel E. Bowser’s top aide on health-care issues is returning to the Child and Family Services Agency for a third stint leading the long-scrutinized department that investigates child abuse and manages foster care.

Deputy Mayor for Health and Human Services Brenda Donald has been filling in as the department’s interim head since the last director abruptly resigned in October.

Bowser (D) tapped HyeSook Chung, an advocate for children and women, to replace Donald as deputy mayor. At a Monday news conference at the Child and Family Services Agency headquarters, Bowser told staffers that she was surprised when Donald requested to return to her old post.

“Not many people come to their boss and say, ‘Boss, I don’t want that job that you promoted me to, I want the other job that I had,’ ” Bowser said.

But Donald thought she had more work to do after leading the agency under former mayors Vincent C. Gray and Anthony Williams, overseeing a push to reduce the number of children in foster care in favor of keeping families together.

The agency has been monitored by a federal court since 1993, the result of a class-action lawsuit alleging that the District had failed its most vulnerable children.

Advocates for children and the independent court monitor have said that the District’s progress has stalled in recent years.

The District’s attempts to end court monitoring faltered after the 2008 case of Banita Jacks, convicted of killing her four children, highlighted the city’s continuing struggle to safeguard children at risk.

On Monday, Donald vowed to make significant strides in the next year toward meeting the remaining goals to end federal oversight. They include more quickly closing child abuse investigations and increasing the number of visits by social workers to troubled families.

“We are driving our agenda to be the best child welfare agency in the country,” Donald said. “We will get out of the lawsuit when we do all of things we need to do.”

The most recent report from an independent court monitor last week credits the agency for more quickly investigating child neglect, monitoring children in foster care and avoiding short-term home placements. But it noted that since July, 10 children spent the night at agency offices instead of foster homes.

Donald said those overnight stays were not because the District lacked foster homes but because of special circumstances including teenagers who refused to go to their assigned placements.

Even some critics of the District’s child welfare system have praised Donald as an effective leader.

“She probably moved CSFA farther in her tenure than anyone else in the history of CSFA,” said Judith Sandalow, executive director of the Children’s Law Center. “She believes you get out of lawsuits by actually helping kids.”

As the mayor’s point person on homelessness, health care and human services since she took office 2015, Donald has grappled with several controversies.

The chief executive of the District’s public psychiatric hospital resigned after a month on the job amid questions over his qualifications, including turmoil at the last hospital he led and questions about his accreditation. Donald had interviewed him for the job.

Donald was also a key player in the mayor’s plan to shut down the homeless family megashelter at D.C. General and replace it with smaller facilities throughout the city. The City Council substantially rewrote the plan after concerns over the costs and benefits to the mayor’s political donors.

And Donald sat on the board of the D.C. Trust nonprofit that was supposed to hand out millions in taxpayer funds for programs benefiting at-risk youth, but declared bankruptcy and folded this year after mismanagement. Bowser praised Donald for her handling of the aftermath to minimize disruptions to youth program.

To succeed Donald, Bowser chose a longtime advocate with a data-intensive background to help streamline how the city serves its most vulnerable.

Since 2009, Chung has led D.C. Action for Children, a nonprofit advocacy group with a data-centric approach to public policy. She says she had government experience earlier in her career working on heroin addiction and child welfare policy in Massachusetts.

As an advocate, Chung has used data to criticize District education policy, although she recently defended a controversial plan to change how the city assigns nurses to schools.