Flight Instructor reported the student lost control of the aircraft during landing resulting in a runway excursion.

Narrative

Training flight; potentially 6th flight total for the student pilot. Instruction was provided on landing after coming back to the airport from a successful lesson in the practice area. Student was on the controls with me as we came in; normal pattern; descent; and landing. As we were in the ground roll; I told the student that we needed to start transitioning our primary controls from the yoke to the rudder pedals. The student began adding too much pressure to the rudder pedals and brakes; and control it was becoming difficult. My reaction was to repeat relax 3 times until the plane was beginning to drift left; followed by saying my controls to attempt to take full control of the aircraft. I was unable to relinquish the students controls on the rudder in time; and we continued our ground roll into the grass on the left side of the runway. No lighting; signage; or other obstacles were hit; the grass was not damaged either. We came to a controlled stop in the grass; and control tower called the go-around for the following training aircraft. I quickly regained control; consoled the student; and called the tower to inform them that no assistance was required; everyone was okay; and that we would taxi off of the runway onto taxiway 1. After exiting the runway; we continued to the flight school and verified that there was no damage to the aircraft.