Wow, this was harder than expected. It's almost like the education theory people don't talk to psychologists. There were some studies that claimed to measure conscientiousness, but it wasn't apparently related to Conscientiousness, so who knows? Maybe they were measuring zombie!conscientiousness?
I trolled the obvious sources for thirty minutes and came up with:
Kim, E., & Schniederjans, M. J. 2004. The role of personality characteristics in web-based distance education courses. Communications of the ACM 47(3):95–98.
Schniederjans, M. J. & Kim, E. 2005. Relationship of student undergraduate personality characteristics in a total web-based environment: an empirical study. Decision Sciences Journal of Innovative Education 3(2):205-221.
Bassili, J. N. 2006. Promotion and prevention orientations in the choice to attend lectures or watch them online. Journal of Computer Assisted Learning 22:444-455.
Good luck, brother. I hope other people have better luck.
I jailbroke those refs (except for #3 which is already online) for my first draft version of a full essay: http://www.gwern.net/Notes#conscientiousness-and-online-education
I've wondered for some time now what the effects of online education might be on gender and income inequality, specifically as online education interacts with IQ and Conscientiousness (compared with offline education). I ran into a study of a course done online and offline that found correlations with Conscientiousness, which prompted me to start writing out my thoughts: https://plus.google.com/103530621949492999968/posts/aKa3qLatwZ3
The model/argument I give (towards the bottom) is logically trivial, and the basic idea seems pretty intuitive - offline classrooms remove some need for self-discipline/Conscientiousness and performance is more g-loaded - that I'm sure I can't be the first person to think of it.
Does anyone have statistics or citations handy which might help in any essay I write on the topic?