Chicago Mayor Rahm Emanuel’s longer school day got a little shorter Tuesday. The longer day has been a centerpiece of the mayor’s education agenda. From the beginning, his administration insisted the day be 7.5 hours long across the board, in elementary and high schools. That’s drawn protests from some parents.

Emanuel announced Tuesday he’s dialing back by a half hour for grammar schools. They’ll all have a seven-hour day, Emanuel said.

The mayor said he listened to parent and teacher concerns, but he is not compromising on his original goal of more time.

“If you don’t start with a goal, we’d be stuck with 5 hours and 45 minutes and 170 days, and that’s unacceptable for the kids,” Emanuel said.

Hear WBEZ education reporter Linda Lutton talk with host Melba Lara about the new proposal for a seven-hour school day.

Emanuel made his comments in the Northwest Side gymnasium of Disney 2 magnet school, one of  13 “pioneer schools” that adopted the mayor’s 7.5-hour day this school year. Flanked by principals and parents from the pioneer schools, Emanuel lauded his administration’s push for the longer day, and downplayed the fact he was revising his controversial original proposal.  “We are gonna go from 170 days to 180 days, from 5 hours and 45 minutes to 7 hours. That comes to 40 additional days of instruction. That’s 8 weeks more of learning,” Emanuel said.

The new day will give grade school kids recess; many don’t have it currently. And it will add nearly an hour of instruction. It will also give teachers more prep time, according to the mayor’s office.

The high school day will be seven and a half hours, a half hour longer than the current day. High school students will be dismissed 75 minutes early one day a week to give teachers time to plan.

A coalition of parent groups said they’d keep fighting to shave off more time from Emanuel’s proposal. They said Chicago Public Schools doesn’t have the money to fund a quality curriculum for a longer day.

“I think as a parent and as a taxpayer it’s reckless for any amount of extended time when there’s no funding,” said North Side parent Tracy Baldwin, who co-founded the citywide parent group “6.5 to Thrive” to fight Emanuel’s original proposal of a 7.5-hour day. “We can’t even fund the day we do have, and I think this is going to be a disaster.”

Baldwin says she cares about quality of school, not quantity. Emanuel said that’s a false choice. He says his new proposal will help raise achievement and graduation rates. Parents this week accused CPS of “spinning” the research and exaggerating the benefits of a longer school day.

Another parent group, Stand for Children, is vowing to hold the mayor to the 7.5 hours he originally promised. That group organizes low-income and minority parents and says a silent majority of parents actually supports a 7.5 hour day.