> When I was a young student (around 12), my math teacher came-up with an unique requirement for his students to not only solve math problems but also to compose them.

I think this is highly underestimated: there seems to be some sort of a duality between learning & teaching, where you can't really practice one efficiently without the other.

This has been observed in part by guys like Feynman[0]; paraphrasing: "learn a topic by teaching/simulating teaching it to a child", which in addition to the above, demands for the topic to be explained in simple terms.

[0]: https://fs.blog/feynman-technique/

“Compose” in the sense of “create”, not in the sense of “combine”

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