Starting next school year, the expanded day includes mandatory recess, which is something many students have gone without for years.
Besides recess, the guidelines call for a big chunk of time devoted to reading, writing, math and science.
While most educators and parents support the idea of more instructional time, some principals worry about the logistics involved in implementing a longer day, and teachers say more time should mean more money.
Students at Bethune Elementary have been going to school for 7 1/2 hours a day since November. The West Side school volunteered for the longer day, and so far, Bethune's principal says the move has paid off.
"We're actually starting to see some changes in our children's development," said Bethune principal Zipporah Hightower.
Next year, all Chicago Public Schools will move to a longer day, and for the first time, CPS is instituting guidelines for principals to follow. There will be an expectation of a certain amount of instructional time for reading, writing, math and science.
In addition, all elementary students will get 45 minutes of lunch and recess.
"It's a way for us to create standards across the city and way to hold principals and schools accountable to student needs," said CPS CEO Jean Claude Brizard.
Fourth grade Bethune teacher Erin Koehler Smith can already see the positive benefits of a longer day for her students, but she says teachers must be compensated for it.
The amount of work we see, it doesn't seem right we are not getting that equality in pay," said Smith.
While teachers are trying to negotiate for more money, the new guidelines call for teachers to take a 45-minute lunch break and to be at school just 10 minutes before students.
Disney Magnet School Principal Dr. Kathleen Hagstrom worries about the logistics: Who will watch the students during teacher lunch breaks? And how will her 1,600-plus students get in the building in just 10 minutes?
"Central office is making decisions that are well intentioned, but don't understand the ramifications on how it will be handled on the school level," said Hagstrom.
Based on the guidelines released Monday, principals have until February 24 to submit a plan to CPS on how the longer day will work in their schools.
Brizard is convinced citywide test scores will go up in a short period of time.
As for current longer day schools, the numbers will not be available until next fall.