Students are introduced to the work of Piet Mondrian as we discuss balance, shape, composition and primary colors. Students are given six 12" black strips of construction paper to arrange on white paper (9x12). Three must be horizontal and three must be vertical. I encourage them to vary the space between their strips/lines so that there is variety of size in the squares and rectangles that are created when the lines overlap. (So many students want to arrange their lines in a perfect grid. A number of them want to put the lines right on the edge of the paper, too, so watch out for that.)
Then students use only red, yellow and blue crayons to fill in only six of the shapes in an effort to create a balanced composition.
The examples below are from first grade.