The commercial pilot was practicing stop and go landings in a tailwheel-equipped airplane with the commercial air taxi operator's chief pilot aboard. She said during the first landing, as the tailwheel touched the runway, the airplane veered sharply to the right. She applied left rudder, but the airplane exited the runway to the right. As the airplane left the runway, she relinquished control to the company chief pilot in the right seat. During the runway excursion, the right wing came up, and the left wing struck the ground, structurally damaging the left wing. An examination of the tailwheel assembly found no anomalies.