What defines form?

Form:

is space, both negative and positive, materials and context.  Positive and negative space are very important parts when thinking about form and 3D objects.

Function:

is a more intellectual thought process

Both form and function go hand in hand and can be very complex.  In the classroom we talk about "art" and not "design."  It is important to bring design into the classroom.  Example: today we are going to design new scissors - using different objects to cut up paper, perhaps for a collage.

Andy Goldsworthy is a very good resource for elementary art.