Capability can be pursued when a teacher REPEATEDLY fails to meet the professional standard required. There is no way it could be invoked after one poor set of results for one group. Have you checked how those particular students compare in your subject compared to their otehr subjects? Business Studs tends to attract weaker, less motivated students so they may have underachieved in otehr areas too. Keep your chin up - there isn't a teacher among us with long service who hasn't had any results disappointments in their career - the STUDENTS have failed their exam, not you!