In the mathematical world, CAS stands for computer algebra system, not creativity, action & service.

Any calculator (I prefer the word "device") with CAS is not allowed to be used on an IB exam. But, in my opinion, this should not mean that an IB maths teacher never uses CAS (handheld device or computer software) as a teaching tool - or does not consider guiding his/her students to use CAS when appropriate.

Ah, but that begs the question "when is using CAS in an IB maths class appropriate given that it's not allowed on an IB exam?" I certainly accept that many (most?) teaching IB maths would answer that question with "never" - but I disagree.

How about just one example to illustrate why I disagree.