 Why are the grey helmets necessary?
"Full psi precautions?" asked Dorffman. The first was from Roberts Bros., announcing another shift of deadline on the book, and demanding the galley proofs two weeks earlier than scheduled. As director of psionic research at the Hoffman Medical Center, he had long since learned how administrative detail could suck up daytime hours. It bore the letterhead of the International Psionics Conference: Dear Dr. Lessing: And the more they struggled, the thicker and more impenetrable the bramble bush became— But now David Lessing had discovered a pathway through that jungle, a theory to work by— At his elbow the intercom buzzed. "If the papers you've already published are a preview, we think it's false as Satan."
 The helmets block external psionic forces.
 The helmets block external psionic forces.  The helmets improve the reception of external psionic forces.  The helmets are for safety, as the children are heavily medicated and at high risk for falling.  The helmets amplify the childrens' psychic abilities.