Daniel Weinreb has a short investigative piece about why MIT's well-known 6.001 course based around SICP and Scheme has been replaced with Python:
I’ve been seeing mail and blog postings, particularly from people in the Lisp community, why MIT has switched from using Scheme to Python in the freshman core curriculum for the department of Electrical Engineering and Computer Science.
At the International Lisp Conference, Prof. Gerry Sussman gave a short impromptu talk explaining the new freshman curriculum. Just to get a second opinion, I later called Prof. Jacob White, one of the designers of the curriculum and lecturers for the core courses. He confirmed Gerry’s description.
Asking why they changed languages is, in some sense, the wrong question.
Also discussed previously on LtU here.