According to this article there is little difference between online learning and inclass learning for science classes.

http://www.insidehighered.com/quicktakes/2012/10/22/study-little-difference-learning-online-and-class-science-courses#disqus_thread

Be sure you read the comments, which point out that this is a press release, not a summary of the study. The students in the study who self selected for the online courses were better prepared academically than those who took the traditional course. So the study is not really valid. And someone who has read the study writes that,

For Chemistry, at least, the data apparently shows there is a difference. From the report: "Results show that cumulative GPAs, cumulative credit hours completed, and Chemistry grade are statistically significantly different for students in either online or traditional Chemistry classes. Online Chemistry students have on average higher cumulative credit hours completed and GPAs compared to Chemistry students in the physical classroom. Students completing Chemistry classes in the traditional format have statistically significant higher grades in these classes compared to students in online classes."

To summarize, students in the online chemistry course had more college experience and had previously done better academically than those in the traditional course, but despite this, the students in the traditional course did better.