Flight Instructor reported during departure roll they observed the airspeed indicating zero resulting in rejecting the takeoff and taxiing back to the flight school.

Narrative

My student and I were cleared for takeoff on RWY XX @ ZZZ; looking to do some laps in the pattern. We took the runway; applied full power and started our takeoff roll. With every takeoff; I call for my students to check for Oil Pressure; Temp And Airspeed; to verify that we are in the green range for oil; and airspeed is beginning to build. We approached the halfway point down the 2000 foot runway; which is our typical rotate location in a Cessna 172; at 55KTS. My Student and I both looked at the airspeed Indicator; and noticed It was still indicating 0; and we aborted the takeoff. The plane naturally lifted off the runway as we were pulling power to idle; and we reached approximately 5 feet in altitude before the aircraft settled back on the runway. I took control of the aircraft; applied brakes; and came to a stop toward the end of the runway. There was no damage to the aircraft; the runway; or any injury to us. We taxied back to our flight school parking location via our own power; and informed out company of the issue.