In my school district in southern Arizona, it starts in July. Unlike when I was a kid, they now have a few weeks vacation in the fall and again in the spring, in addition to all the vacations I had as a kid.
They also have a lot of days where the teachers work and the kids are off, unlike when I was a kid. So if you keep the same number of days of kids in class, and add a lot of vacations...
My ex-teacher sister figured they added 6 weeks worth of vacations and teacher-only days of class. So school starts 6 weeks earlier than before. Mid-July.
In az they may as well be in school in the summer. It’s too hot