The mayors of Grapevine and Southlake have apparently brokered a deal that will keep proposed gas wells away from Grapevine High School.   Southlake Mayor John Terrell says XTO Energy and the property owner seem to agree with a plan to move their proposed well sites.  The original site was less than a thousand feet from the school.  Terrell credits good communication between the two cities.   Because the well sites are in Southlake, Grapevine city ordinances have no effect on them.