[cben]

[Python is great; my comment is only within block-based languages] For those actively teaching¹, consider Snap! (https://snap.berkeley.edu/) over/after Scratch. It's nearly a superset, similarly "low-floor" but much "higher ceiling" powerful language.

Data structures, control structures/message passing, functional programming... It's really "Scheme in Scratch clothing" under the hood.

In particular, its "build your own blocks" facilities are powerful enough (including macros i.e. custom control structures receiving "body" arguments as unevaluated lambdas) for you to build any scaffolding they need to focus on concepts you want them to learn at this stage.

¹If you don't have much time to sit with them, Scratch may win on "go find tutorials on youtube".