Don't be afraid to take the your students outside for a field trip to help them learn a lesson.
EXAMPLE: Next I took the kids up the hill to our apple trees. With some small pruners, I pruned off a few branches while explaining to the kids that I had a plan for these trees. I knew that in order for the apple trees to reach their full potential, they must be pruned. It's probably unpleasant for the plant. But I'm the Master Gardner, and I can see the future somewhat and can tell which branches will compete with each other or are sick. We talked about the symbolism of this, too. I told them the famed CS Lewis / George Macdonald story about God building a palace where He can reside, not the cottage you had in mind.
"Imagine yourself as a living house. God comes in to rebuild that house. At first, perhaps, you can understand what He is doing. He is getting the drains right and stopping the leaks in the roof and so on; you knew that those jobs needed doing and so you are not surprised. But presently He starts knocking the house about in a way that hurts abominably and does not seem to make any sense. What on earth is He up to? The explanation is that He is building quite a different house from the one you thought of - throwing out a new wing here, putting on an extra floor there, running up towers, making courtyards. You thought you were being made into a decent little cottage: but He is building a palace. He intends to come and live in it Himself." C.S. Lewis, Mere Christianity