"Giftedness" is basically whatever people want it to mean. It's not like there is an official regulating body that defines these things. The 'average' score for most IQ tests is something like 90-110. Above that is obviously, literally, 'above average'. How far above average you have to get to be 'gifted' varies depending on who you talk to. In the states most gifted programs don't even use IQ scores, and the hard-to-get-into gifted schools seem to want somewhere north of 130, from what I've read.
Your daughter definitely appears to be at least a little above average, and it does seem like she's under achieving if she's getting C's in English. Have you talked to her & the teacher to see what the problem is? Is she distracted in class? Not turning in assignments? Spacing out on required information? That's the sort of information that's going to best help you, I'd think.
I'd also remind you that a bad/mediocre teacher can lead to really, really depressed scores. I grew up nearly always in honors/advanced classes, but I had a few years where I made C's in various classes... for various reasons. I had one math class that was so boring I never paid attention, and instead read books the whole time. As a result I hardly ever had the work completed or homework... several 0's will bring down your grade pretty dramatically. I also managed to get a C one 6-week period in English because I simply hated the teacher. (I realized I was shooting myself in the foot after that, hah.)
Last edited by epoh; 09/08/12 06:25 PM.