Novel material. If your son is decoding books he's never seen, that's a sure sign that he's reading.

I'm hesitant to say that seeing him read often is a requirement, especially for children on the young side. I have a stealthy little guy who will read in his head and occasionally come out with a full sentence out loud. He's done this ever since he first started reading about a year ago and, to the casual observer, it would seem like he can't read.

What is to give light must endure burning.