C150 flight instructor with student reported a NMAC with a GA aircraft while maneuvering. Flight Instructor took evasive action which resulted in descending close to the ground; then returned to safe altitude.

Narrative

I was the CFI aboard an instructional flight in a Cessna 150. At the time of the incident the student was flying; practicing ground reference maneuvers at approx. 1000 ft. MSL (700 ft. AGL) in the vicinity of the ZZZ VORTAC. While in a level left turn; I observed an RV-6A very near to us overtaking us on the outside of the turn; turning in the same direction we were. As I pointed the aircraft out to my student; the RV abruptly pitched up and begin to roll. I am unsure of the aerobatic maneuver they were doing but they climbed at a pitch greater than 60 degrees as they rolled towards us; and rapidly climbed outside of my field of view. My concern was that they were doing a loop or barrel roll and may come back down on top of us. As I was unable to see them and unsure of their trajectory; I took control from my student and rapidly descended the plane to ensure that we would be below of the RV when they recovered from their maneuver. I am unsure of the altitude I descended to; but it may have been as low as 500 ft. MSL (200 ft. AGL). I remained at that altitude as a did shallow S turns to allow my student to turn and search for the RV. Once he made visual contact and confirmed that they were no longer a collision hazard; I climbed back to a safe altitude.