They can have school or cancel it altogether.
CMS leaders said with more than 10,000 bus stops and buses making triple routes, they're just too big to coordinate a delay.
But that could be changing.
Superintendent Peter Gorman said they're now exploring the option of delayed starts.
He said he's tasked the transportation department with figuring out whether it's possible to delay school.
"One of our other challenges with a late start is how do we feed everyone in that condensed period of time," said Gorman.
Some larger schools in the district serve lunch for three hours so everyone is fed.
CMS took a snow day Monday, which means students will have to be in class Feb.15 as a make-up day.
If they call off school for another snow day, Memorial Day will be used as a make-up day.
After that, any make-up day would dip into spring break.