CHICAGO (CBS) — Mayor Rahm Emanuel is turning his campaign for a longer school day up a notch, while some parents and teachers argue that A 7 ½-hour day is just too long.

So why is the mayor focused on that number?

Few dispute the Mayor’s claim that the current school day is too short, but there are those – teachers and even some parents – who feel his proposed 7 ½-hour day might be too long.

CBS 2 Chief Correspondent Jay Levine spoke to the mayor about it, during a visit to a South Side school that made the grade in a big way, despite shorter hours.

“With the shortest school day and the shortest school year in the country, we are shortchanging the kids and the teachers from achieving what they need to achieve,” Emanuel said.

The mayor visited Lindblom Math and Science Academy in Englewood on Tuesday to make good on a promise to its principal.

“He said we’re gonna make it onto the … top 50 high schools. I said, well, if you do it I wanna come back and I wanna congratulate you and congratulate the students and the teachers for your accomplishment,” Emanuel said.

Lindblom, once a troubled school, made the biggest jump of any school in the state, all the way to number 43 – despite the current 5 hour 45 minute school day, much shorter than top 20 ranked schools in Highland Park, Naperville, Wilmette and Barrington.

With the mayor’s proposed 7 hour 30 minute day, Chicago would go from the shortest to the longest school day in the state.

“There’s nothing magical about 7 ½ hours, but there is a curse at 5 ½,” Emanuel said.

So why did he pick 7 ½ hours as his goal for CPS?

“The reason is that’s what Houston was doing and that’s what the bar was for all the major cities throughout the country,” Emanuel said.

Most Houston public schools have a 7 ½-hour day, though some turnaround schools there are in session for 8 ½ hours for four of the five schooldays a week.

A CPS advisory committee which met Tuesday night is wrestling with both the hours and the make-up of Chicago’s longer day.

One member of that committee, the parents’ group “Raise Your Hand,” surveyed its members.

“Parents are concerned about having time for outside school activities, family time, homework, things of that nature,” Raise Your Hand member Amy Smolensky said. “They think that a 7 ½ hour day is simply too long for a lot of children, particularly younger children.”

Pressed for why he’s pushing specifically for 7 ½ hours, Emanuel said, “The basis of that was when I looked at New York, Boston, Houston, Los Angeles, Miami, all the other cities around the country, we were on the bottom.”

“And our kids have big dreams. They have big potential and I’m not gonna be the mayor that shortchanges them that, which is how this educational system is set up,” the mayor added.

Emanuel has dropped in unannounced at dozens of schools in recent weeks.

Convinced that fixing the schools is the key to economic success for the city, he’s clearly drawn a line in the sand. But the success of Lindblom – without any extra time – might show that time spent in class is only part of it.

It also might lead to a debate, not over whether our kids need more time in school, but how much more time.

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