Over four years ago, Mayor Bill de Blasio’s administration began a high-profile investigation into whether thousands of children in some ultra-Orthodox Jewish yeshivas were receiving basic secular education, including lessons on how to read and write in English.

But then, the release of a report on the investigation mysteriously stalled. On Wednesday, city investigators revealed a major reason for the delay: “political horse-trading” by City Hall.

The long-anticipated report by the Department of Investigation and the Special Commissioner of Investigation for the New York City School District found that while Mr. de Blasio’s administration did not violate the law, it did interfere with its own education department’s probe into the yeshivas.

On Thursday, the Department of Education finally released its own report. The findings were sobering: Only two of 28 yeshivas that city officials visited are offering secular education that is considered “substantially equivalent” to classes found in the city’s public schools.