I can't be too specific but one site in particular that I maintain has a big user base in education (from nurseries to universities) and I think it's very likel

I can't be too specific but one site in particular that I maintain has a big user base in education (from nurseries to universities) and I think it's very likely that this heavily influences the IE stats. I know from experience (I've worked as tech support in schools and a college) that these establishments are normally the very last to push out upgrades to things like browsers. There's a big "if it works, don't touch it" attitude.