General aviation Instructor reported a runway excursion on landing during a tailwheel training flight. The aircraft bounced upon touchdown and the instructor took control and maneuvered back onto the runway without aircraft or airport damage.

Narrative

During tailwheel transition instructional flight; I was the instructor in the back seat and the pilot receiving instruction was in the front seat. Pilot made a normal 3-point (touchdown on mains and tailwheel simultaneously. The plane touched down then rose back into the air; yawing to the right about 30 degrees. Both of us applied full power for a go-around. It was a warm day and we had been flying with the left window open. I had been flying with a loose fitting cap under my headset. When full power was applied; the wind blast came in through the window and knocked my cap back; taking the headset and my glasses with it. This startled and distracted me enough that I failed to straighten the airplane out to align with the runway center line. As the airplane started to accelerate; it touched down; unfortunately headed off the runway. When I noticed this; I chopped the power to idle and pulled the stick hard back to keep the tail on the ground. As we went into the dirt; the airplane started decelerating rapidly and I then added power and steered us back on the runway. I then returned control over to the student while I fished out my gear from the floor of the airplane. Luckily; there was no damage to the airplane and no runway lights were struck. This was entirely my fault for not straitening out the airplane. I'd like to think I'm experienced enough that I wouldn't have been startled but apparently not. This event was terribly embarrassing and just proves that no one is immune in an event like this.