Kids in school are stuck with butts in chairs (and often also at home in front of the TV or computer...) and chairs from an early age- including car seats, etc- frequently are shaped to mold them into a C-curve of sitting on their sacrum instead of their ischial tuberosities. This creates long term problems for the spinal support and sets up people to become one of the many struggling with back pain. So this is the simple method my son and I figured out for learning how to sit on a more supported pelvis.