My Grade 6/7 students did this Birch Tree water colour art;
Water Colour Birch Tree Art

Here are a few pointers to a successful art class;
1. Use water colour paper.  At first, we did not use water colour paper and the paper that we did use was too thin.  It ripped and wrinkled when it got too wet.  Also, paint seeped underneath the tape because the paper bubbled under the tape when the paper got wet.
2.  Before sticking the tape on the paper, stick the tape to clothing or a rug to make it less sticky.
3.  It is very important to lightly outline the tape at the bottom of the page that is in the snow so that you know where the tree ends and the snow begins.
4. Make sure that the horizon line is not evident through the tree.  As you can see, the student's art below this does not follow this rule.
5.  Adding the shadow down the length of the birch tree is very effective, so do not let the students go ahead and put markings on the tree until they have created the shadow effect.
6.  Talk to your students about the angle of the shadow that is cast in the snow and explain why all the shadows should be in the same direction.