The student pilot reported that the accident occurred during the sixth landing on his initial solo flight. He had remained in the traffic pattern while conducting full stop landings. He stated that the wind shifted from a right quartering headwind to a direct left crosswind at approximately 8 knots. While landing, the airplane banked to the right and departed the right side of the runway, encountering a ditch adjacent to the runway. The airplane sustained substantial damage to the right wing. The pilot commented that he might have used the wrong rudder pedal in his attempt to maintain directional control. He stated that there were no failures or malfunctions associated with the airplane prior the accident. The local wind condition was recorded at 6 knots or less during the 2-hour period surrounding the time of the accident.