C172 Flight Instructor with student reported partial power loss during initial climb. Flight crew returned to departure airport and landed.

Narrative

After a normal rotation at normal maximum RPM range (2400-2500 RPM); during the initial climbout; the aircraft experienced a partial power loss (loss of RPM) from about 2400-2500 (normal operations) to about 2300 RPM. I took controls from my student and called the tower to return for landing due to a drop in RPM. Then; while turning to right downwind for runway XX; the RPMs began to drop more to about 2100-2000 RPM; which was not enough to sustain even level flight. I asked tower if runway XY was available and then stated I was requesting priority handling; they stated yes and cleared me to land runway XY. I landed runway XY and then asked tower if they wanted me to call them to discuss. They said yes; I copied the phone number; got clearance to taxi; taxied to park; then proceeded to call. I gave my report and thanked them for their assistance. No services were needed. Oil temperature and pressure remained in normal operational ranges. A&P is investigating RPM drop and has confirmed the aircraft isn't producing appropriate power at this time.