It is a misconception that incoming MIT freshmen know programming. Some of them might (and a few of them will be world class programmers), but these classes are designed for people who don't know programming, at all and believe it or not great majority will be people who never coded anything. I TA'ed SICP in both MIT and Berkeley (they have a pretty similar class derived from original SICP book, some parts of it is in Python, some in Scheme, some in SQL) and most students believe these classes are for geniuses or for people who already know programming. Wrong, the whole point of SICP is to teach it, and once students try hard they see for themselves that they can learn programming.
That's true, but all of them have/had a lot more "mathematical maturity" than most programming 101 students today (who are often middle/high school students, university students who didn't do particularly well in high school mathematics, or even independent learners coming to programming from non-STEM backgrounds).
SICP is not an introduction to programming as much as it is an introduction to computer science.
I mean, one of the key lectures is about differential calculus. Do you realize that at most universities, CS 101 students are not assumed to have taken calculus. Hell, a large fraction of CS 101 students will NEVER take calculus (non-majors who will instead opt for college algebra).
But that example itself is actually more of a red herring. The point is that the mathematical maturity does provide a lot of extremely useful background thinking/problem-solving skills that most CS 101 students haven't yet developed and will be developing for the first time in CS 101.
