Rahm Emanuel is lucky that schoolchildren can’t vote.

Chicago’s Mayor-elect has plans to extend the public school day by as many as 90 minutes and add an additional 10 days to the school year - an unprecedented increase for an entire school district.

The proposal might not be popular with kids, but extended learning time (as it’s known in the jargony world of education policy) is supported by many experts, lawmakers and educators, who see it as an integral tool in improving educational achievement -- especially in schools with high populations of low-income students.

"There’s really very few downsides to extending time for kids because they need academic support and because they need to be safe," said Timothy Knowles, director of the Urban Education Institute at the University of Chicago and a member of Emanuel’s education transition team.

But it’s a simple solution that requires careful planning. Schools can optimize the extra time in different ways and teachers, who are ultimately responsible for the learning going on inside schools, aren’t necessarily on board. In Illinois, legislation currently before the House would give Emanuel the ability to mandate a longer day, bringing the issue to a head in Chicago.

Case Study: Rauner College Prep
The Chicago public school day is notoriously short. Elementary schools have 5.13 hours of instructional time and high schools have 5.6 hours. Meanwhile, the national average is 6.3 hours, according to the National Center for Education Statistics. Emanuel’s proposed 90 extra minutes would put the city above the national average.

In some Chicago charter schools, an extended day is already a reality. At Rauner College Prep High School in the West Town neighborhood, the day runs from 8:30 to 4:00, with 90-minute classes. The school year is also two weeks longer than the regular Chicago Public Schools calendar.

Ellen Sale, a 31-year-old teacher at Rauner, says the class time is "sacred."

"I would cover much less content if I didn’t have 90 minutes of instructional time," Sale said. "I’m able to conference with every student."

Her last class begins as the school down the street is getting out for the day. Afterwards, she holds office hours or works with school clubs.

The schedule also affords Sale 90 minutes of prep time each day. Once a week she uses that time to collaborate with other tenth grade teachers, a meeting she says is important for her development as a teacher.

"I don’t think teaching is a gift, I think it’s a set of skills and some teachers are more skilled than others," Sale said. "I don’t think you develop these skills just by going to a conference."

While teachers are doing prep work, students take electives like band, physical education and ROTC.

At Rauner, 87 percent of the students are low-income, 10 percent are special education and 4 percent are Limited English Learners. Last year, the school scored average in reading and science and above average in math. Chicago Public Schools gave it the highest performance rating.

Proponents add that a longer school day also serves a public safety function by keeping kids off the streets. In April, the dangers of after-school life were highlighted in Chicago when a 12-year-old boy was shot in the back by a 14-year-old rival as class was let out for the day.

"Parents in middle-income and upper-middle income are not interested in having an expanded day," said Cindy Brown, vice president for Education Policy at the Center for American Progress. "It’s very popular in low-income neighborhoods where parents are working and would like to have their kids in a safe place."

The Devil is in the Details
Schools nationwide are experimenting with expanded learning initiatives and in April, Sen. Tom Harkin (D - Iowa) introduced the Time for Innovation Matters in Education (TIME) Act. The legislation is modeled on a Massachusetts program that provides funding to schools that add 300 hours to their calendars. Many of the schools use the time to meet individual student needs, according to Chris Gabrieli, chairman of the National Center on Time and Learning.

"There’s not a whole lot of low-income students who are going home to Tiger Mom or a tutor," he said.

People like Gabrieli have two main concerns: that the extra time is used wisely and that teachers aren’t pushed to their limits. In Chicago, Knowles says an 18 percent increase in time probably wouldn’t mean an 18 percent increase in pay.

But that’s not the only reason some teachers are skeptical of plans like Emanuel’s.

Jennifer Johnson, a 29-year-old teacher at Lincoln Park High School on Chicago’s North Side, says the idea is too simplistic for the complex issues at play in a public school.

Her students already pack seven or eight classes into their schedules. Some have jobs, some take care of younger siblings, and some are simply chronic truants.

"We have so many problems just keeping the kids inside the building," Johnson said. "Increasing the length of the school day or even the school year is not a panacea."

Karen Lewis, president of the Chicago Teachers Union, says she supports extra time if it’s used for activities like recess, arts and music.

"I am not for expanded test prep time, I am not for expanded drill-and-kill," Lewis said.

Emanuel hasn’t yet said how the extra 90 minutes would be used.

"I think if the state law passes there’s gonna be a window open in a way there never has been before to get kids prepared for college," said Knowles. "It’s a really important moment for Chicago."

All statements and opinions expressed on this blog are those of the individual contributors, and not of the Bill & Melinda Gates Foundation or NBC News.