Do you have the SuperCollider Book? Iannis Zannos’s chapter on the language is really good. It isn’t a tutorial, more of an encyclopedia, but well described with occasional examples.
I’ve never looked at SmallTalk documentation, so maybe it exists there, but I personally think there are a lot of great educational materials around Processing.
And it’s similar enough that aside from a few syntax things, being generally a bit more strict about everything, and the fact that the main action happens within a repeating loop, not evaluated line by line, it should get the same mechanisms across.
Daniel Shiffman is an incredible educator within this space, and has videos that go from intro to coding to much more complex algorithmic processes. https://www.youtube.com/c/TheCodingTrain/playlists - is his youtube channel, if you scroll to the bottom there are intro to processing videos. He also wrote a really good intro to processing book that was based on a class he taught.