This went much smoother the second time I taught this. I gave the kids a copy of the ASCII codes the day before introducing the lesson and had them list a minimum of 5 patterns, trends, interesting points, etc. Most of the students recognized the significance of there being 128 codes and commented that that lent itself to 8-bit binary.
The day of the lesson I connected to myself on the Wire and demonstrated sending bits using the binary, decimal, and ASCII boxes. I demonstrated how setting the chunk size was essential to receiving coherent data.
The evaluation for this is another show down: I separate the two-person teams and have one send formatted text that I’ve prepared in advance. The receiver uses colored pencils to write down the message sent. We go over the how they will annotate formats such as italicized and bold. It works well.