By Dana Kozlov

CHICAGO (CBS) – A monumental change is in the works for Chicago Public Schools. All 400,000 students may be headed to classes year-round, on a brand-new calendar for everyone.

One line in an e-mail from Pritzker Elementary School’s principal leapt out at parents: “If all schools go on one track …”

Principal Joenile Albert-Reese confirms CPS officials are considering putting all students on one school calendar – replacing the “two-track system” calendar that exists now.

“I don’t think parents are ready for it. This is going to be a major shakeup for parents’ schedules,” Julie Woestehoff of Parents United for Responsible Education tells CBS 2’s Dana Kozlov.

Currently, some students start school in early August while others start in September. Pritzker’s principal says the focus is moving all students to more of a year-round schedule with strategically-placed breaks.

CPS officials say a calendar change is being discussed, but nothing is final.

“The issue is how many new things do you want to try at once?” Chicago Teachers Union president Karen Lewis says.

Still, Lewis and other education advocates believe moving all kids to the same calendar makes sense. Parents won’t have kids on different school schedules.

But there are concerns, like keeping students cool in schools without air conditioning if they start the year earlier in the summer. CPS officials say it’s all being discussed.

“If you’re going to make a decision, the earlier you tell people the easier it is to make a transition,” Lewis says.

So when will CPS make a decision about next school year’s calendar? Shortly, says a spokesperson.

If the year-round approach is adopted, it could mean the end of the almost three month summer break that most students have now.

But watchdogs hope the final decision is made only after parents and teachers have a chance to weigh in, too.