GMing your squats up?

[Markus]

Im doing high reps on olympic squats (3x10) and as I get fatigued I tend to instead of just coming up, let my ass shoot up and then GM the weight. What gives? Weak abs? What do you recommend to correct it?
I have a backround on olympic lifting, so it's definitly not a technique problem.

[Mark Rippetoe]

One of the problems with high-bar (olympic) squats is the long lever arm formed when the bar is placed on top of the traps. This and other reasons causes me to recommend low-bar squats. You can do more weight without jacking up your low back, directly train your hamstrings more effectively, and get stronger. This issue is dealt with in SS:BBT.