The highest I can PROVE by photo is close to 6'
However, I have gone close to 7.
Your leg makes me insanely jealous, Allison. I've been working on my legs for years and it hasn't been until recently (after a solid 6 months of almost entirely dressage work) that I don't feel like my legs are flying behind me in the wind (that might be a slight exaggeration).... but even so, they certainly don't look like yours!
The highest I've ever jumped was about 4'3" (topped out our standards), but I was young and stupid and should not have been jumping that high. I was lucky enough to be riding and old point and shoot schoolmaster and a few of us decided to play 'Chase Me Charlie'. Needless to say we got a talking to once our trainer found out ;]
The highest I've actually trained at is 3'6", and recently no higher than 2'6", as I fell in love with an older quarter horse with no previous english training and way too much spunk. Also, until last week, I had no arena or jumps to use.