To get the most accurate answer to your question, I suggest contacting the school directly. If located in the U.S., you can use SchoolFinder to research the school's phone number: http://www.education.com/schoolfinder
If the school is closed for the summer, you can call the school district office. School district telephone numbers are also included in SchoolFinder.
Below are some additional resources you may also find helpful for preparing for back to school. Thanks for asking!
I tried to call the school and got a recording that said call back in August with no other option available. No district office information available. Not much help of any kind. It should not be this hard to find out when the first day of school is so we can plan accordingly.
I'm sorry to hear you weren't able to reach someone at the school. You didn't mention the city and state of the school, so I can't provide the district's telephone number via SchoolFinder (the district's page is hyperlinked on the school page and includes the district's telephone number). You can also try a Google search - many school districts have websites that include contact information.
Another option is to ask other parents with children at the school (who may have received the new school year calendar with the end-of-year materials). Your town's Recreation Department may also know the answer. My town's Recreation Department manages the on-campus childcare before and after school, so they do know the school year calendar.