Depends on the school district. Mine usually starts mid Aug, but my sister’s school starts after Labor Day. The later you start the later you get out for the summer. Also if you are a new teacher the district may require you to report early for training/inservice. That could take a week. Plus we have a law in CA that requires all teachers to complete a 40 hour course in reading, language and math each time a new textbook is adopted by a district, so you maybe required to take that as well. Generally, between mid Aug and Sept. 1st is when school starts.
San Diego Public Schools start September 8, 2009. See the attached schedule for the school year here.