The Chicago Teachers Union is rejecting a proposal to immediately lengthen Chicago’s school day.

Chicago Public Schools wanted 90 more minutes of class for elementary schools this year, an idea schools CEO Jean-Claude Brizard floated on TV this week. He said the district would somehow find the money to give teachers 2 percent raises — if they’d accept longer days.

Teachers union president Karen Lewis says they won’t.

“They’re asking us to do 28 percent more work for 2 percent—so doing the math, it’s not coming out,” said Lewis.

Lewis acknowledged Chicago parents may be in support of more class time for their children, but she said that isn’t the whole story.

“Chicago parents also believe we should be appropriately compensated,” said Lewis. “We’ve done the polls too. So yes, they do want a longer day, but they’re not expecting us to work for free.”

The district says Chicago kids get 166 fewer hours of instruction each year than the nationwide average. The union counters that more time doesn’t guarantee better student outcomes.

Meanwhile, Mayor Rahm Emanuel met with pastors Thursday and encouraged them to address the issue in their sermons. He wants them to push for a longer school day and a longer school year.