UPDATED 01/09/12 1:25 p.m.

CHICAGO (CBS) — Two Chicago public schools and 38 charter schools will be spending an extra 90 minutes in class Monday, joining 11 others that have already done so.

As CBS 2’s Susanna Song reports, the schools have stretched their day to 7 1/2 hours, in a pilot program that will be costly, but for which Mayor Rahm Emanuel and CPS chief executive officer Jean Claude-Brizard have been pushing.

LISTEN: WBBM Newsradio’s Bernie Tafoya reports

Making the change Monday are Genevieve Melody Elementary, 412 S. Keeler Ave.; and Benjamin E. Mays Academy, 838 W. Marquette Rd.; as well as 38 charter schools, according to CPS.

At Mays, where Emanuel and Brizard were on hand for the first day back at school after the winter break, the additional time will be spent on individual instruction time and core subjects like math.

LISTEN: WBBM Newsradio’s Craig Dellimore Reports

Some parents question if 7 ½ hours is too long to spend in school, but Emanuel said most parents don’t.

“I was here at pickup time, when they voted for a full school day and parents could not be happier with a full day of education. In fact, many parents have asked for longer,” Emanuel said.

Overall, CPS says, Chicago grade school students are receiving 22 percent less instructional time than the national average.

Under the pilot program, students will spend more time in core subjects such as mathematics, reading and science. But it will also leave time for such options as art classes and recess.

On the CBS 2 Morning News Monday, Brizard reiterated what he believes is the importance of the longer school day.

“I’ll give the mayor credit for starting the conversation. I’ve always been a proponent of a longer school day, a fuller school day, a longer school year, but I’m glad to see it happening here in Chicago,” Brizard said. “Let me give you an example – of the schools that started back in September, they’ve added the equivalent of nearly a month of school in six months.”

Brizard said test scores will not come until the spring to compare performance at schools that have implemented the longer school day with those that have not.

“But think about this – if you want to be a better basketball player, how do you make that happen? Practice,” Brizard said. “So 17 more days – the equivalent of it – adds a lot more practice for our kids.”

CPS is spending about $75,000 per school plus monetary incentives for teachers. The total pioneer pilot is expected to cost several million dollars.

The decision to extend the school day has led to friction between city officials and the Chicago Teachers Union. The union says the day is just too long when teachers aren’t receiving a pay raise to compensate.

The conflict heated up further when Emanuel and Brizard urged schools to break ranks with the union and go ahead with the longer school day on their own. The schools that complied received an extra $150,000 in funding from CPS, and teachers at the schools received $1,250 bonuses and 2 percent raises.

The union then sought an injunction to block the longer day from taking effect this year. Teachers Union president Karen Lewis argued that Emanuel and Brizard violated the union’s contract by allowing some schools to break ranks.

But the union abandoned its push for a court injunction, after the city agreed not to lengthen the day at any additional schools this year.

By next fall, all CPS schools will adopt longer school days.

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