Different style of mask
:D The schools would point out, rightly, a helmet is a head-covering and a mask is a face-covering. Not all helmets cover the face and not all masks cover the mouth. Nowadays, school administrators don't bother with such reasoning. They write "the rules" vaguely, interpret them arbitrarily, enforce them selectively and expel students who don't comply.
Or this - A mother's face is the first a baby sees when entering the world. Wearing a mask while holding a newborn will affect the mother-infant bond as well as the baby's communication developmen