For 11 and 12 year olds. 

Contrast is the Polar Opposite of two things.

Paint two paintings — the subject of your choice — each in contrasting colors. 

For example, when I did this, I painted a mountain landscape in red and a second in blue. 

Make the paintings as identical as possible, but in different colors. Size should be 18″ X 22″ or bigger.

When the paintings are dry, cut one painting into 1″ horizontal strips. Cut the second painting into 1″ vertical strips. Weave them using a basket weave (Google How online), until your two paintings are woven together into one.

Remember, this is all about you learning Perspective.