The XYZ of the W sitting position

Do you have a child or student who sits like this sometimes? This W sitting is named because of the shape the legs make. It is advised that you correct this sitting position immediately as it is bad for the hips, knees and feet as well as for gross motor development. I say to these children that the W sitting position is not the best one and then I explain to them that legs crossed is good for growing bodies. Once they have learned this I say "Legs crossed for healthy feet" whenever I see the child revert to W sitting. The prompt reminds them how to sit as well as reminding them why.