Aeronca Champion flight instructor with student reported their wing tip struck the propeller of another aircraft during taxi. Instructor returned to original spot.

Narrative

I was instructing a student pilot in an American Champion 7ECA Citabria. I was sitting in the back seat and the student was sitting in the front seat (tandem configuration). This was the student's second lesson in the aircraft. From the starting position on the ramp; there was an aircraft located 90 degrees to the right and another aircraft located 45 degrees to the left. The ramp area was marked with centerlines to help maintain separation from other aircraft. I exchanged controls with the student prior to initiating taxi from the parking spot. The student taxied the aircraft forward an estimated of 5 feet; conducted a check of the brakes; and proceeded forward another two feet (estimated) before beginning a left turn. During the turn; I noticed the wing approach the propeller arc of the aircraft that was parked initially 45 degrees to left. Though the wing tip appeared like could potentially hit the propeller; I assumed that my judgement may have been in error and believed we would maintain separation on the centerline.The left wing struck the propeller of the parked aircraft; causing about an 8' tear in the fabric under the wing near the wing tip. I informed the student; and then I took control of the aircraft and taxied into the original spot. Though I believed the aircraft was on centerline; we may have been offset to the left and I failed to see because of my position. It is also possible that the aircraft taxied forward so far that it placed the arc of the wing in the path of the propeller. The student was looking in the direction of the turn and did not have the experience to be cognizant of the approaching collision.To prevent re-occurrence; pilots may tow the aircraft to a clear area if unsure about the aircraft's separation with other aircraft.In the past year; I had primarily been training and flying with students who have at least a commercial pilot certificate; and I had been operating the aircraft from the front seat. The student pilot with whom I was flying was the first pre-solo student I have trained in awhile. Instructors should seek out training and counsel from experienced instructors after significant lapse in teaching pre-solo students (or any student with a lower level of proficiency).