In Python we can revert the overriden operators by casting the output back to the expected type. I don't know if you can do something similar in Ruby.

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Description updated

Tests clarified.

Took me long enough, but I fixed it.

Excellent kata, totally uplives it's goal.

Ideas:
You could specify: "if the same student has multiple scores saved, keep only the highest score" or some such.

"Why should I favour [1,2] over [1,3]."

Definitely agree here. There is no way to know which score should be stored for student 1 (when integers are used as names instead of strings). Please fix this. Otherwise a great little kata.

Other than the examples, do you think it's neccessary to add clarification in the description text?

The code for these classes is pre-loaded, so you should have access to them. I've just tested this across the supported languages, and am able to confirm this is working as expected.

Good catch. I removed that test from the example test cases.

Same for my in Python. I had to define them in my code (luckily, I'd done the previous two, so I sorta knew what he was going for).

Same for Australia. Two Hundred and Five would be 205 not 200.5
I don't think I've ever met anyone or read anything that would interpret it otherwise.

We pulled call_count out because it just complicated the framework and it didn't seem like it was being used. Did you have a use for it?

Added this test! Thanks @joshbrodienz!