Biggles;
Your son wouldnt necessarily need outstanding grades to get an apprenticeship, my GCSE grades were nothing to shout about but I managed to get on one. Having been down the college route and then the apprenticeship I would say that IF he wants to get into aircraft maintenance the apprenticeship is the better route of the two, certainly with respect to getting work experience on live aircraft and being paid to 'learn your trade' is always a bonus.