After you've created your Google Site, you need to change the permissions on your website in order to make is accessible to parents and students. To do this,

  1. Go to your website
  2. Click on the blue “share” button in the upper-right corner
  3. In the “Who has access” section, it might indicate that “Specific people can access”. Change this to “On – Anyone with the link”. Save your changes.
Now parents and students can access your website.