Lastly, you should check out Open edX’s cohort feature which allows you to assign students randomly to a group, so maybe you could make use of that feature to match the groups of 3 students.

http://edx-partner-course-staff.readthedocs.org/en/latest/cohorts/index.html

Here are some resources you can use to develop a little training program:

http://files.edx.org/Getting_Started_with_Studio.pdf (online version of this guide is herehttp://edx.readthedocs.org/projects/edx-partner-course-staff/en/latest/)

http://files.edx.org/Overview_of_Creating_an_Online_Course-V1.pdf

You can also take the demo course on edX.org to see some of the capabilities of the platform.

https://www.edx.org/course/demox-edx-demox-1

And this edX 101 course explains how to author a course on the edX platform:

https://www.edx.org/course/overview-creating-edx-course-edx-edx101

There are also some demo courses:

Stanford: https://class.stanford.edu/courses/StanfordOnline/OpenEdX/Demo/info

edX: https://www.edx.org/course/demox-edx-demox-1

And some good materials from Berkeley: https://berkeleyx.berkeley.edu/wiki/