Repository for Education
As it seems unlikely at this point that this question will receive an appropriate answer soon, I'll answer my own question and give the best answer I came across.

Someone who is in Education research has told me that he and his colleagues use Academia.edu and ResearchGate. So, while there are certainly repositories out there, it would appear that they are not widely used. In the end, I recommended to the author of the thesis that they use these two sites.