Inconsistency in the quality of staff performance can be the result of a whole range of factors. An unexpectedly poor examination result is not necessarily the direct result of poor teaching. It could be because of resourcing decisions made two or three years previously. It could be pupil grouping arrangements dictated by timetabling constraints. It could be the result of external pressures on either the teacher or the pupil. Once detected, the determination of the reasons for poor staff performance is a complex exercise.