We moved here from California and our previous school had the same issue. They resolved it by having year round school but breaking the school up into three separate groups that rotated during the school calendar. This meant that one group was on break while the other two attended class (thus cutting the in school population by 1/3). Everyone LOVED it especially since there was no long summer where kids didn't retain their education or got bored and it was also helpful to two working parent families. Families also took advantage of "off season" vacations as kids always had a break with each season.