Schools in the United States are usually closed part or all of June, all of July, and part of August. Most schools are closed between Christmas and the day after New Years Day, and for a week in either March or early April. There are some schools that have school year round, so the times they are closed vary from this.
They probably were not closed for a month in 1973 or 1977, but they may have been closed that long in 1978 due to the 1978 blizzard.
To find out how many schools were closed a previous week, you could look in that week's newspapers for schools that were closed in your area.
Schools were not closed during World War 1.
No they are not closed.
Closed
If New York City schools are closed, they would be closed on the third Monday of February for Presidents' Day.
Any kind of schools can be closed permanently or temporarily due to emergencies or weather.
Schools are not closed for Lincoln's birthday, though many are closed for President's Day.
no
Schools are not usually closed on Halloween.
To find out how many schools have been closed in 2013-2014, you would need to check newspapers or call schools to find out if they have beeb closed.
Oklahoma City Public Schools are closed only because the subject is plural and must have a singular verb "are."