Some things to think about when considering a later start to the school year:
1) The second semester would be much longer than first semester (though second semester does include several testing days). This could impact final exams.
2) High school graduations would be pushed back to later in May (they now typically are held in the middle of May).
3) Spring semester finals would take place after Memorial Day
4) Some weather make-up days, which are now scheduled after Memorial Day, would be pushed into early June.