Welcome sfb! I tend to think GT-ness in very young kids can be hard to tell. My 7 year old certainly did not present as wildly gifted until at least 5, at least in my eyes. He was intense, but his interests weren't necessarily very academic. He wouldn't play alphabet games with me (although hindsight, I'm sure he knew a lot more than he would let on. I never pushed this kind of thing.), but he would happily spend an hour figuring out the plumbing system in our house. Or we'd need to stop and analyze complex gutters on buildings. He could play games for older children.
I think in young kids, it can be more about intensity than about actual academic knowledge and achievement. My 4 year old daughter's interests happen to be much more classically academic - reading, alphabet, absolutely begging to practice piano after her brother. Her preschool teacher absolutely love her and talk about how precocious she is. I didn't get ANY comments like that from her brother's preschool teachers (although I certainly get them now). But after watching her brother develop, I just doubt she's MORE gifted. Just a different personality. And neither of my kids is likely as wildly gifted as many children on this board either.
Anyway - there is probably no way to know how GT your child is until they are ready to be fully tested, but watch and wait! I think the going in streaks on interests is very normal. And if your 6 year old is hitting ceilings on subtests, he is likely quite gifted!
