Initiatives like Saturday lessons and after school revision lessons tend to be introduced by Headteachers and their senior management teams. It enables them to claim they have done something to improve results, even if they aren't even sometimes on the premises when these extra sessions occur. Unfortunately these initiatives rarely seem to be reviewed. They are harder to stop than start for political reasons. The staff delivering them are often put under different types of pressure to carry them out. The suggestion I would make is to never start doing them. Some people say they will for an additional payment (that can have the same effect).