Barnaby Smith, of Oakleigh Crescent, Godmanchester, sat the test in November - five years early and scored 97 to secure an A*. His sister, Polly, who is 15, took the same paper and achieved the same grade, although by one mark less than her younger brother. Proud mum Sarah, who teaches her children at home, said: Barnaby seemed to be so quick on the uptake with maths when he was younger. He said the more complicated his maths got, the more he liked it. I thought he would catch up with his sister, so when she was working towards her GCSE maths, I taught them together. He was quite confident and I wouldnt have entered him for it if he wasnt going to get a good grade. The siblings sat the exam, an International GCSE, or IGCSE, at Cambridge Centre for Sixth-Form Studies and received their results on Friday (January 24). I was really excited and really proud of them, added Ms Smith, who said she chose to teach her children at home to give them a custom-made education to suit their ability. They both did so well. Barnaby, who has two other sisters, Eleanor, 18, and Alice, 23, and a brother, Oliver, 27, might sit his physics GCSE next summer, and possibly French, said his mum. When hes not studying, he enjoys playing on his games console. He also enjoys tennis, running, Scouts and amateur dramatics with Spotlight Productions. As for the future, he has his sights set on a university place at Cambridge, where he wants to study ... maths, of course.