I think also, its better to teach I/O expansions technique with standard logic circuits like 74LS138+74LS541 for inputs and 74LS238+74LS573 for outputs.

Then after this was managed, the next step could be, using the 74LS165 and 74LS595 for I/O expansion.

Then maybe the next step was implementation of both methods inside a CPLD.

For education it was recommended to use the more robust 74LS series instead the more sensitive 74HC series.


Peter