GT kids tend to do things in strange orders, so hold the worrying. My daughter was not interested in reading early. However, she wanted to write. Since then, I have heard of quite a few GT kids who write before they read. She began reading (or the interest of) afterwards and now is a huge reader.
Her Kinder teacher (who I loved) was perplexed, but went with it and did not push the reading and let her write. Her first grade teacher (who I also loved) let her learn cursive and once she mastered that, her reading accelerated several grade levels in a few weeks. They had both been around gifted kids quite a lot and learned to "go with the flow".
I guess she had to do it her way. If anyone would have forced her to read first, I have no idea of the outcome so no data there. I guess she needed depth to the symbols.
