Part of our rock unit covers volcanoes. I have found this model to be something fun to have, but not needed. You can always draw a volcano on large chart paper and do a cutaway to show the inside.
I also have this book. If you teach about volcanoes, you should really get this book. It has amazing illustrations and it's well written. The children love it!
This week we'll be making a paper volcano model and will use model magic to make the magma and lava. I'll post pics and directions next week!