Family court judge Ronald Richter was tapped by Mayor Michael Bloomberg on Wednesday to take over the Administration for Children's Services — bringing with him an intimate knowledge of the child welfare agency that some think could help it during this difficult time.

Richter, previously a top ACS official, was a former Legal Aid attorney who represented abused or neglected children.

"There will be no learning curve," said Bill Baccaglini, who runs foster care agency The Foundling. "Ron will hit the ground running. He knows the courts. He knows the system. He knows City Hall so you gotta be happy about that."

It's a difficult time to take over ACS. The Brooklyn District Attorney has been investigating the agency following the death of a 4-year-old girl earlier this year. Two caseworkers were indicted in the case for allegedly failing to properly monitor the child and falsifying records.

Richter said one of his first priorities will be to use data to determine whether child protective workers are using all the tools at their disposal to properly protect children.

The newly appointed commissioner also said he plans to draw on his experience as a family court judge to ensure ACS, the family court and other agencies are working together.

"As a judge you are really deciding people's lives and deciding their futures and he takes that work very seriously and he always has," said Gail Nayowith, with social service provider SCO Family Services. "And I think that puts him in a wonderful position to be able move this system to the next level."

As head of ACS, Richter will oversee not only child protection but also Head Start programs, the juvenile justice system and city subsidized daycare system.