I am not sure if this was mentioned, but someone forgot about snow days. In my district on Long Island, we have a contractual calendar for 184 days. In addition to that there are 3 nights that are required. (meet the teacher night and 2 nights of parent/tecaher conferences). If we get hit with a good amount of snow or ice, the schools will close, due to the fact that many kids come to school via bus. Two snow days are built into the calendar. If we lose them to bad weather, it's not a big deal. If it doesn't snow, we eat them. If it snows for more than 2 days, certain vacation days get eaten away...such as those during the April vacation. That makes planning a trip hard to do and planning a vacation without paying peak prices impossible.
In New York City, the schools almost never close. That is because quite a bit of Federal and State funding is based on children who recieve free breakfast and free lunch. If the schools can't open, it's alleged that these kids won't eat.
I'm sure that the folks in Florida, don't worry about snow days, but you must close down for hurricanes. The people in Iowa must worry about twisters. I will presume that these are predictably seasonal.
Out here, most of the rooms aren't air-conditioned. It would take too much money to provide the wiring and the necessary units to deliver comfortable temperatures. Only the computer room, the library and the Principal's office have AC. Research has proven that when it gets too hot, children will not learn as well or behave as well as they would if they were comfortable. Add to that graduation rehersals and summer school and you can bet that it is a sweatbox. It might be cheeper to shut down for the summer then to install and run ac units.
Just a thought.