I read about a boy who achieved an A* for GCSE Maths at the age of 7 today and a girl who got a C grade at the age of 5 which is clearly astounding and reminds me of Roald Dahl's character of Matilda who is my absolute favourite! I love that book and film!
I think as long as there is not pressure on those young high-achievers then it is fair enough for them to sit a GCSE in whichever subject they enjoy or excel in if that is what they would like to do but it is when there is a phenomenal amount of pressure from parents that I think there is a real issue. Five-year-olds are not really supposed to be working out the circumferences of circles or the gradients of graphs. Having said that, who is to say what kids should be interested in? In fact, when I was at primary school age I was probably more content reading an encyclopedia and writing mini articles on the solar system or doing little word puzzles, which is effectively the same as being interested in being academic.
I wish I had enough money to just keep studying lots of different things and then one day write an encyclopedia of my own!