The flight instructor reported that following a wheel landing in the tail-wheel equipped airplane by the pilot receiving instruction, the airplane began to drift left of the centerline. The pilot receiving instruction applied right rudder control inputs and the airplane veered to the right. Despite the flight instructor's control inputs to regain control, the airplane continued to the right and subsequently ground looped. The left wing and horizontal stabilizer struck the ground, which resulted in structural damage to the left horizontal stabilizer. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.