I think that this question ("What age to stop Pocket Money?") is an interesting, and perplexing one. It is necessary, or so is my belief, that this decision is ultimately to be made using mainly the knowledge of the parent, and not that of other people.
I, personally, do not spend much money (other than a computer every few years, although not for a while now), however, if I were required to work for money, I would have to sacrifice school time.
I can only comment upon the "work-load" of the subjects I take (Mathematics, Further Mathematics, Physics, and Chemistry), but at AS-Level (and I presume more so at A-Level), the "work load" is rather high.
What one has to gauge is the positive impact of work with the negative impact that there may (or may not) be on the education of the child. I believe that for me, there would be a considerable impact on my education, however, this will vary from person to person (I believe).
At my 6th Form they do impose a limit (albeit only suggested) of a relatively small number of hours per week of work (unrelated to the education of the child). This is probably based upon experience (or so I am told), and therefore it might be of interest to the original poster.
Work in itself is good education. It is a difficult conundrum for the optimisation. I suggest that the original poster will discuss this with the child, and come to a conclusion that is an optimised (or tending to optimised) solution.
Angus Higgins