Administration for Children’s Services chief David Hansell has launched a full investigation into the hiring of Jacques Edwards, the ex-con now under arrest for assaulting a 6-year-old. Sadly, the city’s probably going to have to review all hirings under disgraced former ACS Commissioner Gladys Carrìon.

Edwards earned his undergraduate and master’s degrees while serving 28 years in state prison for a murder he committed at 19. Somehow, the Carrìon team overlooked that history (which should’ve been disqualifying) and failed to submit him for screening by the state Justice Center for the Protection of People with Special Needs, as the law has required since June 2013.

At least the Edwards bungle didn’t cost a kid’s life. Carrìon’s across-the-board mismanagement helped lead to multiple horrors on her watch — children killed in their homes despite being on the agency’s radar.

After weeks of delay and denial by Mayor Bill de Blasio, that grim record eventually led to her replacement by Hansell, who has spent the last 18 months on wholesale reform — including procedures to ensure that ACS won’t hire anyone like Edwards to work with kids.

But that leaves countless other Carrìon-era hires on the payroll — potential problems that ACS, the state monitor overseeing it and the city Department of Investigation must now rush to vet. How far did her team drop standards in a rush to reduce caseloads that were out of compliance with state standards?

The blame here falls squarely on de Blasio, who tapped Carrìon to head ACS and then ignored outside warnings — from city Comptroller Scott Stringer as well as DOI — that the agency was going wrong.

Years of mismanagement can leave all manner of hidden land mines, even after a competent reformer like Hansell takes over.

Let’s all pray that Edwards proves to be the worst of Carrìon’s remaining legacy.