Parents and lawyers filed suit last year against Cobble Hill Success Academy, which the city now says replaced light fixtures in its shared building last summer without city permission.

Tension between the teachers union and Success Academy Charter Schools operator Eva Moskowitz reached a new high — or low — today, with each side accusing the other of jeopardizing children’s safety.

UFT President Michael Mulgrew said Moskowitz had violated city construction rules, while Moskowitz connected the behavior of union workers to December’s devastating school shooting in Newtown, Conn.

The charged rhetoric stems from a dispute over light fixtures in the Brooklyn building that Success Academy shares with three other schools. Last week, the UFT joined Public Advocate Bill de Blasio, a mayoral candidate, in calling for an investigation into how Success Academy’s Cobble Hill school was rid of light fixtures containing toxic PCBs while the other schools in the building continued to have the lights. De Blasio alleged that the department had given Moskowitz’s school preferential treatment.

As it turns out, de Blasio was wrong. The department did not remove the lights from Success Academy’s portion of the building — Success Academy simply had the lights removed in the course of other renovations, without the city’s approval.  (Moskowitz has said before that a benefit of running a charter school is that she has to pass through less red tape to get the light bulbs she likes.)

That happened over the summer and triggered concern that asbestos or other dangerous chemicals might have been disturbed, according to department officials.

“We have spoken with the Success Charter Network about its contractor completing work that was not approved and will increase monitoring of their projects,” a department spokeswoman, Marge Feinberg, said today.

In a letter to Chancellor Dennis Walcott today, Mulgrew said the department’s explanations of what had happened in the building were not adequate. The Division of School Facilities “apparently does not know how the demolition material was handled or where the fixtures were disposed,” he wrote, amid a list of concerns about whether the renovations had been done safely.

Success Academy officials would not say what kind of permits, if any, they had obtained before having 40 light fixtures replaced over a weekend in the summer of 2012. But Moskowitz said in a statement that concerns about safety were unwarranted.

“The quality of work was done to the highest standards and with the highest level of professionalism,” she said. “No child was put in harm’s way.”

Instead, Moskowitz accused Mulgrew of putting children at risk by allowing union employees to take photographs inside Success Academy’s basement space during the school day on Tuesday. In a letter to Mulgrew, she wrote, “Given the heightened concerns around safety in schools in light of recent violent events, it is unconscionable that the UFT would deliberately violate our school’s security by sending unauthorized strangers to prowl our hallways.”

Ellie Engler, a UFT official, said she and two colleagues had finished a meeting with Division of School Facilities officials on Tuesday when they walked through Success Academy on the way to space that the charter school shares with other schools in its building. When she saw, through an open classroom door, a flush-mounted light fixture — one that would not have PCBs — where she expected to see the old-style hanging fixture, she took a picture with her iPhone, she said.

Moskowitz said Mulgrew’s letter to Walcott was designed to distract from that episode. “Mike Mulgrew is trying to dodge the fact that in the wake of the Newtown shootings that he is endangering children’s welfare by directing his operatives to sneak into schools,” she said.

Success Academy also released a statement from a parent, Natilee McSween, that hammered home the point.

“After what happened in Newtown, how can the UFT put politics ahead of the safety of my child? I am furious that the UFT snuck into the school and put my child’s safety at risk,” said Natilee McSween. “The city needs to hold the UFT accountable.”

Moskowitz has called on Special Commissioner of Investigation Richard Condon to look into the UFT’s entry into her school’s space. And the UFT has asked Condon to investigate whether the city gives Moskowitz special treatment.

Meanwhile, the rest of the building is scheduled to be cleared of PCBs over the summer — just as Moskowitz opens schools in six additional Department of Education buildings.