If an institution (like Harvard or Stifel) really pays for your product, then you should write a case study.[0] That would be effective and honest advertising!

However, unless the institution is paying, you shouldn't use its logo. E.g., if a college student signs up for an account, that's not the same as the college itself using or endorsing your product.

[0] Here's an example case study from Patrick McKenzie (patio11): https://web.archive.org/web/20120211173734/http://www.google...