Consider creating A/B split tests to show different content to groups of students. You can then compare the performance of the students in each group, gaining added insight into the effectiveness of your curriculum.
Note
To learn more about A/B split testing, have a look at the Wikipedia article at http://en.wikipedia.org/wiki/A/B_testing.
You can have multiple content experiments active simultaneously in your course; each experiment can use the same groups, or you can have each content experiment operate independently.
Note
If two experiments share the same grouping, any student in Group A for the first experiment will also be in Group A for the second one. If you want your content experiments to operate independently, you must assign different groupings to each content experiment so that students are randomly assigned to each.
Enabling content experiments requires you to add "split_test" (the internal edX name for a content experiment) to the Advanced Modules List in Advanced...