I lived in KCMO and went to Hickman Mills schools until 7th grade, then I moved to Shawnee Mission. In those Hickman Mills days, there was no spring break, Christmas break was like a week, and school started after labor day. In SM there were longer breaks but an earlier start to the school year. It hasn't really changed much with the calendar since I was in high school except maybe creeping back in August.
What's weird to me is in Seattle my nephews start school in mid september and go to late june. that's weird.