The heuristic I developed is to consider first a repeated phrase, compress it, then a repeated sequence of phrases, and compress those, and to then look for more simple terms and to compress. Generally, I’m looking at large repetition, and then working my way down to less frequent, or smaller repetition.
Students may not know where to start, and so it may be valuable to get them to simply explore the tool and see what they find. As students begin to play, their body of knowledge will grow. Calling out different compression rates of different students may create some excitement and challenge. The challenge will then help differentiate students so that a teacher can then work with students who are not as successful with the widget.