I’d just like to interject for a moment. What you’re referring to as Racket, is in fact, an HtDP language, or as I’ve recently taken to calling it, ISL plus Lambda. HtDP languages are not Racket unto themselves, but rather another pedagogical component of a fully functioning Racket system made useful by the runtime system, compiler, and vital standard libraries comprising a full distribution as defined by PLT.

Many 111 students run a modified version of the Racket language every day, without realizing it. Through a peculiar turn of events, the HtDP languages which are widely used today are often called “Racket”, and many of their users are not aware that they are basically different languages, developed by the core team.

There really is a Racket, and these people are using it, but it is just a part of the system they use. Racket is the kernel: the module in the system that provides a minimal set of syntactic forms and functions for the other programs that you run. The kernel is an essential part of a Racket-based language, but useless by itself; it can only function in the context of a complete language. An HtDP language is normally used in combination with the Racket system: the whole system is basically Racket with a translation phase added. All the so-called “Racket” student languages are really HtDP languages.