MONROE, N.C. -- Sun Valley High School students and staff returned from winter break on Tuesday to freezing classrooms after the building's heating system failed.

Union County Schools confirmed the building had no heat for the first hour-and-a-half of the school day, but it's since been fixed.

Junior Naiva Simpson described the building as "like an iceberg."

"I don't think anyone could concentrate at all," Simpson said. "Everybody was distracted."

Junior Alyssa Swiatek questioned why the school system didn't delay class for Sun Valley.

"You can't really concentrate when you're cold," Swiatek said. "You don't want to pick up a pencil because your hands are cold."

Union County school leaders said crews checked Sun Valley's heating on New Year's Day and found no issues.

When staff returned the following morning to find no heat, the school system said students were already on buses heading to school, which made it too late to delay school.

Both students and parents criticized school leaders for not delaying class.

"If we would've had that two-hour delay, we would've been fine," Simpson said. "Everybody would've been warmed and heated."