Obviously, back in the 1950’s, people simply weren’t smart enough to realize that a flimsy desk wouldn’t protect you from the raw fury of a broken strong nuclear bond. Their Loony Tunes routine just highlights how laughably ignorant they were. Right?
Sure, if you’re in the primary blast radius , you’re pretty much toast. Possibly atomized toast. (Very hard to butter). But outside of the primary blast zone, you’ve got a wave of overpressure that has enough force to shatter stone. The further out you get, the more the pressure front dissipates. Now, imagine that you’re outside of the primary blast radius and that the pressure front isn’t strong enough to rubble the building you’re sheltering in. In this case, a school. If you were hiding under your desk, the school you were in would have classrooms which were all essentially one large open space in the middle of four walls. Four walls, with one lined with windows. Glass windows.