The student was receiving training in crosswind take-offs and landings in 5 to 10 knot wind conditions. For the third take-off in the sequence a minimum ground roll technique was employed. The aircraft lifted off in a slightly nose-high attitude but did not appear to be climbing or accelerating. The instructor took control but was unable to improve the aircraft performance and the right wing and maingear collided with a fence. The gear leg was detached, and shortly afterwards the aircraft touched down in the paddock beyond the fence. The nosegear collapsed and the aircraft slid sideways to a halt. No defect could be found with the aircraft which may have contributed to the accident. Neither the instructor nor the student had noted the engine rpm or the indicated airspeed prior to, or at lift-off. It would appear that the airspeed at lift-off was lower than the recommended speed and that the nose high attitude subsequently maintained prevented acceleration to gain adequate flying speed. Prior to take-off the wind direction was seen to be varying and it is possible that a slight downwind component may have affected the performance of the aircraft.