Next time Mayor de Blasio brags about the city’s rising high-school graduation rates, ask him about the “worthless diploma” fraud that still plagues the city’s public schools — as responses to The Post “Maspeth Minimum” exposé prove.

It’s not just Maspeth HS in Queens that seems to lower any standard that might stop a senior from graduating. Social-media commentary shows the problem’s widespread.

Maspeth whistleblowers told The Post of administrators “fixing” grades and tests. Last Sunday, Thomas Creighton recalled how Maspeth graduated him early though he spent much of his junior and senior years drunk, stoned and truant. “Everything the article said was true,” he told The Post.

Meanwhile, social media has been ablaze with claims of similar scams at other schools. One commenter on Chaz’s School Daze, a blog for teachers, asked, “Can someone name a school not doing this type of so-called cheating?” Another wished for an investigation of Flushing HS, whose principal “brags about the graduation rate going up to 70 percent. . . As long as you have the numbers, that’s all that matters to the DOE.”

Rather than messing with schools that work, Chancellor Richard Carranza should be targeting this educational injustice .