The manager at the flight school reported that, during a training flight, the student allowed the airplane to drift to the right of the runway centerline on approach. He added that the flight instructor reminded the student to remain on the centerline, but as the airplane flared for landing it continued to drift to the right of the centerline. The student applied full right rudder, the airplane "yawed and banked to the left," the instructor pilot initiated a go-around, but the right main landing gear struck a taxiway sign. Subsequently, the flight instructor continued the go-around and landed without further incident. The airplane sustained substantial damage to the right horizontal stabilizer and elevator. The manager at the flight school reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.