If you want the modern, grad-level version of an MIT scheme class, I highly recommend Sussman's 6.945. I don't know if there's an open courseware version but the entire class is centered around psets, each of which starts with a base environment provided by Sussman and the teaching staff, and which you are required to work in / extend. The class itself was extremely entertaining: you watch Sussman walk back and forth between two transparency projectors, switching the slide on each one as he arrives. Yes, you got very good at reading scheme code very quickly while listening to him talk at the same time.
I understand why MIT decided to make the introductory CS classes more accessible -- they wanted to expand the CS department beyond just those who had already had programming experience by the time they got there, I think? It makes a lot of sense and frankly I found the "replacement" classes pretty great, even while I was taking this class at the same time. Instead of going on at length about how much of a shame it is that MIT "got rid of its scheme class", consider 6.945.
This was one of the handful of classes that I felt were worth the price of admission; I've written code differently ever since.