SusanM:

I think about this sometimes (yes, I have too much time on my hands). Does this mean we are all asshole prejudiced people who should go through sensitivity training until every cell of our brain knows better? That people who say they are not prejudiced are liars? Or can it be dismissed as a random glitch, leftover from our pasts that we no longer care about? Do these knee jerk responses matter, even when viewed in light of our much more deliberate actions to the contrary?

I would say they are not liars, as I go with the literal meaning of prejudice, to pre-judge, where I thinking judging takes active thinking, not just a subconscious response. And actually I would go further and say that the immediate brain response has probably developed to optimize efficiency, as the subconscious response is likely correct more often than not (as you say most primary teachers are female). In no way should that discredit the person who then thinks about the topic without prejudice, and comes to a different conclusion than the subconscious response.