Patty, It appears Trulia uses Google Maps, a choice on top of the Google page to map schools. Their information comes directly from an account created by each business (school). To the best of my knowledge, someone with the school needs to login to the account and change the address.
I also suggest, verifying your address on Yahoo Local and Merchant Circle.
If you cannot find your Google account information, try contacting Trulia through their customer service or help links. These are located at the bottom of most pages in the left hand column.
Please keep me informed of your progress by submitting a response on Trulia, I monitor answers to questions. Perhaps another user will be able to supply a better way.