The most likely to occur disastrous events don't have a long duration before order begins to be restored. Natural disasters can be devastating, but most are relatively localized and the response and recovery time is a couple weeks to a month at the longest. Your children might miss some school, but the time is usually made up at the end of the year or possibly by extending the school day.
But every now and then a major event happens, like Hurricane Katrina, that disrupts entire geographic areas and devastates schools.
Katrina completely destroyed 110 of 126 New Orleans public schools, displacing more than 60,000 students. A year later, the school system was only able to accommodate the return of half the students. It is estimated that more than 400,000 students in the Katrina ravaged regions had to move to other cities to attend school.