STATEWIDE (NEWS CENTER Maine) -- School districts all over Maine had to decide whether to cancel, delay, or still hold classes Tuesday because of the bitter cold weather as kids returned from winter vacation.

MSAD 6 canceled classes because the buses would not start.

Noble High School in Berwick announced Monday that classes were canceled due to a burst sprinkler pipe.

Scarborough Schools, RSU 15, and RSU 21 all delayed classes for two hours to allow temperatures to rise for kids waiting at the bus stops.

"I think it was the right call," said Wentworth Intermediate Principal Kelli Crosby. "We have 54 square miles in this town and the temperature is crazy different regarding how close you are to the ocean -- and kids out at the bus stop at 6:30 or 6:40 in the morning -- it was the right call."

Some parents said the inconvenience is worth their kids' safety.

"I don't mind at all. I want our kids safe. I think the delay is smart and being a couple hours late, everyone will understand. It's been a cold week," said Mark Hatch, whose son attends Wentworth Intermediate.

"Students' safety is always first in mind. I think it was probably inconvenient for some families trying to get back in the routine today, but thinking about the safety of all the students is the first priority," said Crosby.

Districts like Portland and South Portland did not cancel school, but sent home notices warning parents that school was still on and encouraging kids to bundle up. Some kids were waiting at bus stops at 7 a.m. with an air temperature of -9 degrees Fahrenheit.

The Mayo Clinic and Maine CDC said frostbite can occur in less than 30 minutes in subzero temperatures.

Bus drivers in South Portland came in before dawn to start the buses and get the warmed for kids.

Superintendent Ken Kunin said Tuesday that one big concern with posting a delay is that a parent or student could miss the message.

"I had visions of kids going out to bus stop at regular time and then bus doesn't come for two hours," said Kunin. "That seemed to be more of a danger than kids waiting out briefly at the bus."

He said he consulted with multiple other superintendents in other districts and facilities managers. Kunin recalled his time spent as principal at Portland's Reiche Elementary and having to help kids who still showed up at school get back home.

Assistant Superintendent of Portland Public Schools Jeanne Crocker said there is no one benchmark, such as a certain temperature, that determines if a school cancels or delays. She said administrators consider a number of factors, including the temperature and the amount of snow.

She said the goal is to make the call as early as is reasonable.