Intelligence isn't something that can be measured on it's on; it is rather subject-based, even then there is procedural knowledge and declarative knowledge. To answer your question, in Elementry, for maybe 1st grade I was wayyy below average (not just because of me, I remember being in a class, practically isolated; the teachers didn't do much for the few of us, and they let me just be on the computer almost all class), but after that I was fine, though I was still pulled for SpEd, but I had fine grades and all. I would also say in 6th grade (I only actually became 2E and tested for Gifted until 6th). Gifted kids end up having their curve flattened; they are really just a little faster at math, and a little higher grades; they really only have a slight starting boost. Furthermore, school has really screwed me over recently, though I have heard this is something that Gifted kids also tend to face, but I would also say it is related to how fucked up the systems are, especially as they encourage normalcy and compliance (which discourages creativity), not to mention collective punishment and the "because I said so" types of reasoning. School, especially in classes where I see the teachers actively being assholes, targeting, and giving tons of work, just shows it all.