Flight Instructor reported a critical ground conflict during take-off roll when a helicopter entered the same runway unannounced from a taxiway further down the runway. The Flight Instructor continued takeoff and flew over the helicopter; narrowly clearing it.

Narrative

On the night of Date at XA:25 local; I was instructing a student in Aircraft X. As we approached the hold short line of Runway XX at Taxiway XX; we heard Helicopter say that they were ground taxiing via Taxiway XA on CTAF. They did not specify whether they were holding short of Runway XX at Taxiway or Taxiway XZ. Hearing this; my student and I announced on CTAF that we were taking Runway XX for a departure to the northeast. After checking both directions on the runway and monitoring CTAF frequency we decided to take-off on Runway XX. As we accelerated down the runway for take-off everything appeared and sounded like a normal take-off until seconds after rotation when Helicopter took the runway for departure from either Taxiway XY or Taxiway XZ. With the helicopter still located in front of us with less than 1000 ft. horizontal distance between the two aircraft and closing; my Student properly took evasive action to ensure we could clear the helicopter vertically. Prior to clearing the helicopter; I reemphasized that we were rotating and now in the upwind of Runway XX. Narrowly clearing the helicopter by roughly 150 ft. vertically we continued in the upwind and departed the area to the northeast. No radio call was made by the helicopter until we had already passed overhead of the aircraft with vertical height being roughly 400 ft. AGL at that point. Could have easily been a loss of life situation.