Keep it very simple! How to get both wheels off, on, and fix a flat. My experience is that even with adults, more than 6 students is crazy. At least half will be standing around because they because they don't understand what we too often take for granted:
- They don't understand the vocabulary
- Not explained why a wheel may come off but no go back on because the forks or frame moved. Or it came off around the fork wheel retention safeties, but the nuts will need to be loosened up more to get it back on.
- Why getting the bead into the bottom of the rim is critical
- If I see something dangerous, I will say stop and if necessary I will take the tools from your hands. A tire lever flying across the room and hitting someone in the eye is much worse than either embarrassment or worry about the touch. Happens because they didn't understand why the bead must be in the bottom of the rim.
- Why inflate the tire to find the hole before the tube is removed from the tire (saves running your hand inside the tire because the tire wasn't clocked to see if there is still something in the tire. A cut finger is no fun. And no, at least in much of the north, you aren't going to find a bucket of water on the side of the trail to look for leak. Ice maybe . . .
- Why over inflating the tube as it lays on top of the tire just isn't a problem to find the hole.
- Maybe mention that by clocking the tire logo and inner tube stem, the next time finding the leak will be much easier.
- How to get the rear wheel of a single speed coaster break back on straight. Hint, pull the wheel all the way back on the brake side, lightly tighten the axle nut, straighten the wheel in the drop outs, and tighten the other side, fully tighten the brake side, Don't be surprised if it looks like the wheel isn't in the drop-outs all the way.
- Buy tools that fit, teach them to use the box end and if an adjustable wrench is used, how not to strip the nut. Hint, adjustable wrenches with turn direction arrows aren't to prevent breaking the wrench, it's the best way to keep the wrench tight on the nut.
So much more than just a quick demonstration 1/2 won't be able to see, understand the vocabulary, or understand right to tight, left to lose.
Just an opinion.Good luck,