CHICAGO (CBS) — A rapid rise in coronavirus cases in the Chicago area is a big concern for some Chicago teachers.

As CBS 2 Political Investigator Dana Kozlov reported, union leaders said that rise in cases is one reason why the school district should pause on its plans to reopen the city’s public high schools on Monday, April 19.

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The Chicago Teachers Union is in ongoing negotiations with the Chicago Public Schools and that call led to some snags Wednesday.

CPS and Mayor Lori Lightfoot are holding firm on keeping April 19 as the date for high school students to return to the buildings. But union leaders now want that plan delayed for at least a week.

“We do not yet have an agreement for safe reopening,” said CTU President Jesse Sharkey.

But for CPS, it is full steam ahead – with some schools already sending emails to students opting to return that tell them what days they will be back in classrooms effective April 19.

Sharkey does not approve.

“We are asking for the Chicago Public Schools to delay reopening schools by a week in order to understand what’s going on with the dangerous spread of the variant,” he said.

The union also tweeted about new positive COVID-19 cases in more than a dozen schools, where students have been back in classrooms for a month.

But a CPS spokesperson called the CTU’s information inaccurate, accusing the union of again “choosing to create uncertainty” for families about school safety – and pointing to its own COVID data.

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But those data show 13 adults and eight students who were in CPS schools last week tested positive.

“We’re at the table right now asking the district to find a way to help vaccinate our high school students and their vulnerable family members,” said Mueze Bawany, a teacher at Roberto Clemente Community Academy at 1147 N. Western Ave.

“I’d love to reconsider that date, but we don’t have enough vaccine,” Mayor Lightfoot said Wednesday.

That is what Mayor Lightfoot said about not allowing 16- and 17-year-olds to be vaccinated until April 19 – a week after the rest of the state. The mayor also acknowledged the rising COVID cases, but is not budging.

“I see no basis for delay, it’s my expectation that we’re going to be opening high schools as indicated by CPS,” Mayor Lightfoot said.

It is a big negotiation roadblock, in addition to the already-present speed bumps.

“Without an agreement, I think that potentially could have an impact on whether or not people in the schools are willing to go back,” Sharkey said.

And that sounds like Sharkey again dangling a strike as a stick. The CTU also fears COVID cases could reach a point that would force all schools to go all-remote again, based on metrics set in the grade school agreement.

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Mayor Lightfoot does not believe that will happen.