The flight was intended to give the student practice at the procedures required in the event of a breakage of the tow line. The instructor released the glider from the tow at about 350 feet above ground level. The student manoeuvred the aircraft towards the strip. On final approach both pilots realised the aircraft was low, but they expected it to land within the confines of the strip. However, the left wing struck a tree some 19 metres from the aerodrome boundary. This impact slewed the aircraft, which then collided with a fence before striking the ground while travelling backwards. The pilot of the tug aircraft had not complied with the pre-flight briefing, which required him to maintain runway heading after take-off. The tug had turned to the right at about 200 feet above ground level. This action placed the glider in a less favourable position for the pilot being checked to employ the standard procedure for returning to the field when the cable break was simulated. Although he was an experienced glider pilot, this was his first cable break exercise for three years and he was not in current flying practice. At the time the pilots realised that the glider was low, suitable areas for an outlanding were available, but the instructor relied on the other pilot's judgment and allowed the approach to continue.