Mandalas are designs that exhibit the concepts of balance and symmetry. I use mandalas to teach those terms and concepts along with being a good review of orderly design.
Here you can see a couple of students doing small sketches(practice drawings) of mandalas.
If you notice, most of the students have written the word mandala, numbered each of the mandalas and in all of the designs you can see the student demonstrating a good understanding of the concept of mandala and balance.
All of the the above are great examples of quick mandala sketches.