I agree with Zhian. A datapoint fwiw: I realised that my DS could read a fair bit when he was about 2.5 (first words, and letter sounds, came much earlier, but I think that's the case for just about all children learning to read). His reading age, as judged by which books he could read straight off, stayed at twice his chronological age as near as I could be bothered to judge it, until he reached the point where it no longer seemed useful to think in terms of reading age since what he wanted to read was not limited by what he could read. This was with noone making any effort to teach him to read, and with him spending 9-5 M-F in play-based nursery: he really did this himself. Which I suppose may be why in maths, where he didn't really take off until he was already at school, his acceleration is more crazy: everyone is encouraging him to work at maths. I suggest you hold your hat....
