When comparing the school data displayed on our site (GreatSchools.org) with the GreatSchools Rating displayed on real estate sites, you should always consider the information on our website to be the most up-to-date and correct. We update our database on a rolling basis every two weeks.
Real-estate sites do license our data and are sent updated feeds whenever changes have been made in our database, but they roll in this updated data on their own schedule and may not have integrated our newest data quite yet. You can contact them directly for information on how often they update, and to alert them of any discrepancies. The same goes for differences between two real estate sites--one may have updated and the other has not. Verify with GreatSchools.org's page on the school and that will be the most up-to-date information.