Following a 3-point landing, the pilot receiving tailwheel instruction raised the tail to initiate a go around, but the wind shifted from a left quartering headwind to a left quartering tailwind. The airplane veered left and the pilot added right rudder and aileron to correct. The airplane continued to veer left, exited the runway, and came upon "tall grass and very rough terrain." The instructor took the flight controls, aborted the go around, and the left wing and elevator impacted the far side of the "trench." The airplane sustained substantial damaged to the left wing and elevator. The flight instructor reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The automated weather observation station located on the airport reported that, about 5 minutes before the accident, the wind was from 240° at 3 knots. The same automated station reported that, about 35 minutes after the accident, the wind was calm. The flight instructor landed the airplane on runway 15.