kfb – The yeshiva is open but warm inside. If you weren’t gonna let your kids outside that day, don’t send them. But if, like you said, it’s dangerous, then they shouldn’t be outside playing either.
I happen to like when my kids get a break so I let them stay home whenever I get an excuse to do so, but regarding your question, our kids school said that IF you have a safe way to get to school, please do so, otherwise stay home. The building was warm and they had extra space heaters.
The school “rewarded” the boys with a day of sledding when the weather warmed.