1. Things happen.
2. Life's not fair.
3. and most importantly, Art is temporary.
oh and my favorites:
4. Air bubbles are your enemy.
5. Nothing should be thicker than your thumb.
How you teach kids those philosophies is up to you and your personality.
For the smaller kids I would recommend not making ceramics where things
"stick off", i.e. arms, legs, etc. and stick to things that are contained
more in shape (i.e. look up "netsuke" for animal shapes), and hollow them
out from the back...or start making pinch pots, which are pretty much
contained in shape.
I teach high school, and they pretty much know my philosopies (above) and
the additional ones of:
1. If yours exploded you get to clean out the kiln.
2. If you made one and it exploded, you can always make another, only