PHILADELPHIA (CBS) — The Philadelphia teachers’ union is demanding the school district come up with a better plan for asbestos remediation. On Tuesday, the union filed its first lawsuit against the district over the issue.

The city says it’s now preparing to step in.

“We want to make sure that people trust the process. And what’s gotten us into court right now is people still don’t have faith that we have a standardized process,” Philadelphia City Councilmember Maria Quinones-Sanchez said.

A standardized process of reopening closed schools is at the basis of the lawsuit against the school district. City leaders are looking to appoint a third party to address asbestos concerns in the city’s schools.

“We’re looking to standardize how we’re going to be dealing with the buildings but I want principals and teachers focused on academics,” Quinones-Sanchez said.

Quinones-Sanchez represents the district that includes McClure Elementary School. Students there haven’t had a full week of school since before Christmas because of asbestos concerns.

In the 45-page lawsuit, the union says the school district failed to comply with its own standards of asbestos testing and remediation.

The Philadelphia Federation of Teachers announced the lawsuit Monday prior to filing it.

The lawsuit claims the district is violating the constitutional rights of teachers, students and staff by not providing safe learning environments.

The lawsuit also refers to a former teacher at Meredith Elementary School in the Bella Vista neighborhood who was recently diagnosed with mesothelioma after teaching in the school for decades.

“It’s a challenge when you’re dealing with older buildings. I anticipate that there’s asbestos in probably more than half the real estate in the city of Philadelphia. The issue is, how do you address these issues?” City Council President Darrell Clarke said.

In the lawsuit, the union says it wants a written plan on how the district plans to respond to asbestos concerns. They also want an agreement in place regarding when closed schools will reopen.

The school district previously said it would spend over $150 million to remediate damaged asbestos. It also says every school has been inspected.

It’s not clear when the lawsuit will be heard in court.