Educational calendars have been linked to "agricultural" time restrictions based on a need to have the young ones back on the homestead for labor. 

This need is outmoded by societies current context and should allow us to revisit the calendar to deal with the modern reality.

Extended breaks should certainly still be a part of the educational program, for student and teacher sanity.  The fierce defense of summer vacation by union interests speaks strongly to the need for some kind of down time.

Seasonally adjusted calendars by region to minimize cost of operations should also be considered.

In the Northeast perhaps the longest break of the year should take place in the winter when it is both more expensive and more dangerous for students and teachers to get  safely to and from school.  In the southwest perhaps it should still be summer months that see an extended break.  In any case the calendar can be reimagined now because we can and some might say we must.