Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [name of principal],
I just wanted to write to say that we're new in the area and that my son/daughter, [name], will be joining your school this fall.
Is there anything you can tell me to help prepare for the school year? I'd be interested in hearing about your school in your own words. How has your experience been there? What have you learned?
Thank you for your help. I look forward to hearing from you!