Some students waited hours before their parents picked them up.
"It was a little distracting but I just tried to do the best that I could," middle school student Ella Anderson said.
Her mother pulled her out of class to protect her health.
"I just didn't want them to get sick," Tammy Anderson said.
At schools like Southwest Middle School in Steele Creek, the staff took a picture of the thermometer in the classroom when school started. The gauge showed it was 50 degrees.
CMS promised it was working on the problem.
"Teachers and students are being relocated to warm areas to continue learning throughout the school day," CMS officials said.
When parents like James decided to take his children out of class, the district told him his students would still be penalized for taking an unexcused absence.
"It's not positive for the teachers,” James said. “It's not positive for the students. Things break. It's unprecedented. Schools aren't set up for this so I'm not mad at anyone. Just want to be reasonable and make sure kids have the learning environment they need."
By late morning, CMS said the boilers were working at Mint Hill Middle School. It also said the majority of the issues at other schools had been fixed.
Still, many parents are waiting to see if the district will also resolve the unexcused absences.