I haven't looked enough into Smalltalk's history — thank you for the pointer! Although the "language levels" I'd mentioned previously are implemented with macr

I haven't looked enough into Smalltalk's history — thank you for the pointer! Although the "language levels" I'd mentioned previously are implemented with macros, the underlying concept is a little deeper than that and I don't know of an earlier example of such a system! Certainly the Lisps and Schemes did a lot of macro work, but they did not tailor applications of that work to CS education in the same way (to the best of my admittedly limited knowledge).