Starting point for me would be volunteers bring their own bikes in that are attending the class. Even among seasoned adult riders, so many have horrible brake and shift adjustments. Be it the pads and derailleur adjustments themselves or the ergonomic reaches and positions of the levers on the bars.

With that, #1 would be stopping. Setup the levers to the user's finger reach. Then square away the pad/rim clearance and toe of the pads. Then move on to "moving" forward. Safety of the RD and FD limit screws.

One tool though for this that almost no joe bike person or even seasoned racer often ever owns that is gold is the "third hand" or "fourth hand" set of cable pullers. Which is probably why so many bikes have such lazy brake pull and somewhat vague shifting even on nicer bikes.

Otherwise...........changing a tube with just the roadside tube, levers, and hand pump. An essential skill many even seasoned weak handed roadies can't seem to do.