In Edexcel IGCSE maths (which seemed easier than Cambridge), an A kicked in at about 62% for the last few years.
It was Edexcel that he took, Not sure where you got the 62% from, he averaged 82% and was given a grade A.
After the IGCSE Higher Maths, he took IGCSE Biology last year in year 9 and also got a grade A in that as well.
He wanted to do another this year but there's not much point whilst he is doing the real GCSE's at school.
He enjoyed the distance learning approach and found both the tutors were very good. Got some great notes to supplement the course material which I think is excellent revision material for later on. he just enjoyed the challenge of doing something a bit different to homework.