Zo’s honeymoon with the teachers union is over.

The boss of the influential teachers union called out Mayor Zohran Mamdani’s administration’s literacy initiative after more than half of city’s public school kids failed their reading proficiency exams.

United Federation President Mike Mulgrew took aim at the NYC Reads program after the embarrassing showing by students in grades 3-5 on their state English Language Arts exam, showing a rift with the labor group and the democratic socialist mayor eight months into his term.

The public salvo also comes while Mamdani weighs whether to sign or veto legislation to boost the pay of thousands of paraprofessionals — a promise he explicitly made at a press conference last year when the UFT endorsed him in his run for mayor.

“The DOE [Department of Education] needs to make sure each school has a clear instructional plan,” Mulgrew said of the NYC Reads phase-in.

“That means streamlining what schools are doing, making sure programs align, and eliminating unnecessary paperwork and assessments,” Mulgrew said. “We’re not going to support it if they want to implement it the way they did this past school year.”

City public school students in grades 3-8 saw a 6% drop in their ELA scores from last year, with just about half overall rating proficient.

The mandated NYC Reads program started under former Mayor Eric Adams and was extended this year by Mamdani and his point man at the city Department of Education, Schools Chancellor Kamar Samuels.

In an interview with the Daily News, Mulgrew complained that supplemental programs added to the main literacy curriculum were a flop, a characterization that the DOE disputed.

During a Thursday press event, Mamdani defended the reading program.

“I continue to be confident in NYC Reads. And it is developed with the real findings of what’s been effective across the country in mind,” Mamdani said.

“And we know that it is a critical thing that we equip our public school students with,” the mayor added. “We look forward to being in conversation with the UFT as we look to not only build upon the successes of the last few years, but to go beyond that.”

Sources said Mulgrew’s preemptive strike is an attempt to get ahead of the fallout from the declining test scores to deflect blame from unionized teachers for the poor showing.

In addition, education insiders said Mulgrew might have bitten his tongue if he didn’t have a separate, smoldering tug of war with Mamdani over pay for paraprofessionals.

Paraprofessionals’ skimpy $32,000-a-year base pay became a hot-button issue last year with Mulgrew rallying on City Hall’s steps to support a bill to raise it by $10,000 outside of collective bargaining contracts.

During his successful mayoral campaign last year, Mamdani appeared at a press conference where he accepted the endorsement of the UFT and promised to approve legislation to boost the pay for paras.

“I will be proud to continue to support the passage of Intro Bill 1261 …. that addresses the fact that there are too many open positions right now for paraprofessionals across the city because that job simply doesn’t pay enough,” Mamdani said then, with Mulgrew standing behind him.

The council passed the controversial $10,000 pay bump last month.

But government watchdogs said Mamdani would set a bad precedent by signing the bill, because it will undermine collective bargaining with other unions who would also run to the City Council to get what they couldn’t win at the bargaining table with the administration.

After the council passed the para pay bill, a City Hall spokesperson said Mamdani’s position was that pay raises were best resolved through collective bargaining, not through legislation — a shift in the mayor’s position from the campaign.

The spokesperson then contended the council’s bill directly violated the state’s collective bargaining law.

Mulgrew said it’s time for Mamdani to deliver a pay boost for paras now, complaining the mayor’s change in tune is unacceptable.

“The school system can’t hire enough paraprofessionals; so our special needs students are not getting the services they are legally entitled to,” Mulgrew said.

“This is costing city taxpayers more than a billion dollars a year in lawsuits. We need to fix this, and we can.”