The flight instructor in the tailwheel-equipped airplane reported that the pilot flying was receiving instruction for a tailwheel endorsement. He added that, during the seventh landing of the day, the pilot extended the downwind to allow for traffic that landed ahead of them. He further added that, during the wheel landing touchdown, as the tail was settling to the ground, a wind gust "turned the airplane's tail," which resulted in a ground loop on the runway. The left wing, engine mounts, and windscreen sustained substantial damage. The flight instructor and pilot receiving instruction reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. An automated weather observation station at the accident airport recorded wind from 240° at 6 knots. The flight instructor reported that the landing was on runway 22.