"Plus" - someone who knows more about the subject than you, has more experience than you, can act as a mentor and resource for you and answer questions.

"Equal" - a study buddy at about the same level as you to work through problems together and challenge each other to make sure you both understand the material. This is the person you go to when you initially don't understand something and you try to figure it out together. If you're both stumped after you're spent some time with the issue that's when it's time to ask the "Plus."

"Minus" - Someone who doesn't have as much experience or subject matter knowledge as you do. You act as a mentor/resource for this person answering questions and explaining concepts. This in turn helps to solidify your understanding of the material.

I've long thought it would be beneficial to incorporate this concept into online learning and your platform looks like it has all of the information to make it happen. In addition to study buddy recommendations would you consider adding the ability to pair people currently taking the class with people who have completed the class who are willing to be a resource? I would guess the "Equal" is the most important component and your system tackles that but there might be significant value to users in adding the Plus/Minus as well.