I think or at least though most European countires had year round school, at least Germany. I believe they had two weeks vacation between quarters or semesters. They also divide the students into those who have colege potential and those who will go into trades at about age 12. I do think the idea of some time between semesters, helps student decompress. Usually, schools have two weeks off during Christmas break in the states. There seems to be a bit renewed interest in going back to school.
Some of the down side, is that it gets hotter over here in the states. I remeber in the 70's getting early out of school around Washington DC, since the temp was above 90 F or 100 F. Usually 85 F is hot in Germany. 90F is a heatwave. This would add to the electrical demand and energy cost to school districts.
There is a charter school starting up around here. They did ask for input. This was one of the points I recomended. Still, with a charter school, you are dealing with a different type of student for the most part. Although, I think one of the charter schools was for vo-tech type of students. Still, I have heard of some vo-tech schools that used to be very selective.
Tom