There's a huge regional variation in when schools start. When I taught in AZ, we started the week before Labor Day and ended around May 30. Now they start around August 10-15 and end at the end of April it seems, or May 1.
Here in MA, there are some districts that start the week before Labor Day and some that wait until after the holiday. It was a *huge* cultural change when some districts started having their year start the week before. But, in years when Labor Day is late (like this year) and there are a lot of snow days, school was not out until almost July 1st a few years ago.
Now the push is to get rid of our "February" and "April" vacations, and have a spring break in March like the rest of the world.
I don't think it will happen in my lifetime.