I think communication with parents is one of the best tools a teacher has available. When there is an issue with a student in your class, if you've had open communication with the parent and they know what is happening in your class, they are more likely to be on your side. If they do not have open communication with you, however, they will almost always side with the student. For this reason I create an email listserv during the first week or two of class. I send home a sheet of paper and the parents may opt to receive updates via emails from me, or opt out of this service. After I've collected all of the papers, I set up an email distribution list in Outlook - yes, this is time consuming but so entirely worth the effort! I typically try to send out an email every other week updating the parents on what their child is learning in class, upcoming tests/quizzes/projects, items that should be coming home for the parents (such as progress reports!), and any special events that affect our class. I will also email individual parents to let them know if their child is struggling in math, has a behavior problem, or has significantly improved recently.
Most teachers likely will not be able to set up this email listserv over the summer as class lists have not typically been released, but I encourage you to create your letter home to the parents or download my pre-created one from TeachersPayTeachers. Also, take some time to learn how to create contacts and distribution lists in Outlook so this process will move quickly when you return to school.
Bonus: In my download I have included step-by-step instructions (with screenshots) of how to make your own distribution list in Outlook 2007!