FWIW, both my kids were very interested in reading/phonics/writing at age 4, and by 4 and a half or 5, knew all the letters and most of the sounds, and could recognize and write about half a dozen words, like their names, "mum", "dad", and "zoo"
But basically they started school at age 5 not really looking any different to anyone else. It wasn't until about 5 and a half they started pulling ahead, and were a year ahead by age 6.
By age 8 they're about 4 years ahead, and university level by 11. They're not especially mathematical.
So, not early readers, pretty much exactly on time readers, but then take off after that. Five and a half doesn't ring any alarm bells but it's great you're aware enough to jump on any problems if there are in fact any.
