It's worked well for ds because it's broken each subject down into topics. Obviously he could do this himself but it saves time and effort imo.
You buy a subject pack that has every individual topic on little magnetised cards, eg: for History you get 'Causes of the Cold War', 'Germany 1930-39' etc, for Biology you get 'Characteristics of living things', 'Female reproductive system' etc. Then we have a big whiteboard divided up into the days of the week and each day has X number of magnetised cards on it showing him what he needs to revise on that day.
I'm sure some dcs probably don't need it but for slightly disorganised lazy ones like my ds it's been really useful in breaking subjects down into manageable chunks. It also means that you can ensure you've revised everything as long as by the time the exam rolls around you've covered everything in the pack.