It may depend on which school(s) your kids will be going to it may be different. I've attached a link to the Everett School District website that would be the best source for an answer to your question.
Here is the districts answer to your question:
When will school start in fall 2012?
The school year calendar is one of the items decided with school staff during contract negotiations. Contract negotiations between the district and Everett Education Association (representing teachers) are underway now.
Traditionally, contract negotiations have established the Wednesday after Labor Day as the first day of school for students. However, that traditional start date can be confirmed only when negotiations are finished.
A school year calendar is very important information for students, families, staff and community. The district will use the website, automated message systems, electronic and traditional media to announce the first day of school as quickly as that decision is made.