The only discernible action the administration has taken based on its desultory investigation has been to pass the buck. It wrote to the state Education Department this month, asking for guidance — something it could have done years ago.

Students at these Yeshivas receive little secular instruction in primary school, and some former students have said boys in particular receive even less after age 13. Administrators at the schools that investigators visited said the yeshivas had adopted a broader curriculum, but they provided the city with only an outline of the material.

In an op-ed in The Times earlier this year, Shulem Deen, who was raised in a Hasidic family but left the community, wrote that his yeshiva education left him bereft of even basic knowledge. He recalled students learning to sign their names in English for the first time at the age of 18, to prepare for their marriage licenses.

Mr. de Blasio told reporters recently, “Clearly there was room for improvement but I have to be straightforward and say there’s room for improvement in a lot of our traditional public schools, too.” Failing to make enough headway in one area is a peculiar excuse for failing to make headway in another.

Mr. de Blasio, who like many New York mayors has benefited from the backing of powerful Orthodox Jewish groups over the years, says he is balancing religious rights with the need for government oversight. “It has nothing to do with political support,” he said in an interview. In retrospect, he said, the city should have moved faster to inspect the yeshivas to which it was denied access: “We’re willing to be as aggressive as the state Education Department would allow us to be.” That’s an oddly passive response from a mayor who has fought aggressively to win control of the city’s schools from the state. And this is not the first time that city officials have acquiesced to demands from these groups, such as easing guidelines around a circumcision practice that health officials felt was dangerous.