The head of Florida's embattled agency for children and families resigned Tuesday, four months after it learned that a 5-year-old girl in its care had been missing for more than a year.

Gov. Jeb Bush immediately accepted Kathleen Kearney's resignation, which is effective Sept. 3.

The Department of Children & Families has been under fire since it was revealed that Rilya Wilson had disappeared while in state custody. The little girl has been missing since January 2001 and no caseworker had checked on her for 15 months.

"I would like to believe that during my stay here it can be said that: she believed, she hoped, she tried, she failed often enough, but with God's grace, she often accomplished more than she rationally could have dreamed," Kearney said in her letter to Bush.

Kearney's only mention of Rilya's case in the letter was to say that her department had been aggressively working to improve the tracking of children.

Bush, who defended Kearney as child advocates and lawmakers called for her to be fired, praised her again after accepting the resignation.

"All Floridians owe her a debt of gratitude for her public service," he said.

Kearney is a former prosecutor and was a juvenile court judge in Fort Lauderdale presiding over child abuse and neglect cases when Bush appointed her in 1999. He had promised during his 1998 campaign that he would solve problems at the agency.

While many applauded Bush's decision, Kearny came under fire as more and more problems at the agency were revealed.

Besides Wilson's disappearance, a caseworker last month filed a report saying 2-year-old Alfredo Montez was fine only to have police find the boy had been beaten to death -- before the worker's supposed visit.

Last month, a child welfare worker was arrested after police said she was passed out drunk in her car with a child in the back seat. Over the weekend, the South Florida Sun-Sentinel newspaper tracked down nine children the department said were missing.

State Rep. Frederica Wilson, who repeatedly called for Kearney's firing, said she hopes Kearney will become a whistleblower.

"Now she places herself in an even more powerful position," Wilson said. "She alone knows all of the agency's frailties. She knows what's broken in the system ... She can help fix them. She can advocate without the fear of being fired or alienating the governor."

Bush did not indicate when he would appoint a replacement.