The certified flight instructor (CFI) was providing tailwheel instruction to a pilot who was going to purchase the accident airplane. They had completed 10.7 hours and 56 landings. The pilot planned to depart the following morning with the airplane owner so the CFI felt pressure to complete the pilot’s training. While practicing three point landings, the wind was gusting to 19 knots. After touchdown, the airplane began tracking to the right. The CFI was guarding the controls closely, but consciously tried to let the pilot recover on his own. The airplane then entered a swerve to the right which he was unable to correct with full application of left rudder and brake. The CFI reported no preimpact mechanical malfunctions with the airplane that would have precluded normal operation.