United Kingdom
It depens what the laws are in your country. Here in the UK - there are specific health & safety laws regarding minimum temperatures for buildings. If a school couldn't maintain the legal minimum temperature, it would have to close temporarily.
United States
Sometimes. If temperaturs are bitterly cold, that and other factors would be considered. If school district administers determine that the conditions pose possible dangers for students, schools could be closed.
To learn how to find out if a school in the UK, US, or other country is closed, visit this question: How_do_you_know_if_your_school_is_closed_due_to_inclement_weather_on_a_certain_day
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