While practicing pedal jams, during third exercise, nose yawed past centre and then got away from the student in control. The helicopter yawed left and rotated two times during which the engine went silent. Instructor took control and settled the helicopter in a hard landing from approximately 8ft. The helicopter’s tail struck ground and then hit heavily on skid deforming it, Helicopter rolled onto its left side coming to rest at a 45 degree angle. Location is well-known approved low-flying area.