I just created a tutorial to encourage my students to try varied line quality in their drawings.
The act of drawing itself is challenging, so it might seem premature to discuss line quality in elementary school. However, students quickly understand the value in this technique when they see how sophisticated their final results are! I compare their pencils to race cars on a track, and discuss how to intensify the lines whenever it quickly changes direction.
This technique has been quite successful with my 3rd-6th grade students, and I hope it will be fun for all of you to try!