Waterbury's Gilmartin School dismissed early Tuesday after cold weather knocked out power to more than 3,000 homes in Waterbury, Naugatuck and Prospect.
Eversource Energy, formerly known as Connecticut Light & Power, said extreme cold caused equipment issues and stressed power lines in the area.
Some 500 students at Gilmartin School in kindergarten through eighth grade were dismissed around 1 p.m. Tuesday after the lights went out and the heat went off.
About 2,100 outages were reported in Waterbury as of 11:30 p.m., and one student said kids huddled in class with their coats on before administrators made the decision to send them home.
"I think it's ridiculous that we just now found out about it," said parent Ralph Holt. "They've been in school since 9 o'clock this morning with no heat."
Parents said even though they had no electricity at home, they had no idea the heat was off at school when they brought their kids in Tuesday morning.
"They didn't tell us anything," said another Waterbury dad, Joseph Delgatto. "We got an automated call from the system about 10 minutes ago that they were closing the area at 1 o'clock."
Waterbury school officials said they held off on making the call because they were waiting on a clear answer from Eversource as to when power would be up and running again. After the estimate changed several times, administrators decided to cancel.
"Luckily for me, I get the opportunity to work from home, so I could mad dash down here and pick her up," said parent Trena Epps. "But wow, it's awful, you have parents who don't have the ability to get their kids now."
As of 11:30 a.m., 2,100 outages were reported in Waterbury, 700 in Naugatuck and 400 in Prospect.
Waterbury officials said power was restored to the Gilmartin School by about 1:30 p.m., just as the last students were leaving for the day.