For what level?
The Elementary, middle school and high school year (over 180 days) usually runs from Sept. to June. There are several "breaks" and they differ according to where the student lives. In our area, we have religious holidays off, Christmas Holiday, Winter break, and a Spring Break.
Colleges and Universities run by semesters; students can go year-round or start in late August/ Sept. to December, then Jan to May.