In the comments section, in the context of whether one is more likely to survive the collapse of a building using the duck-and-cover technique or the triangle of life technique (taking refuge next to furniture, not under it), Jonathan Post tells the following story:

When we had "duck & cover" nuclear drills at my Robert Fulton elementary school (P.S. #8), in the late 1950s, I refused to get under my desk, and got sent to the principal's office. I explained to him that we were directly across the East River from downtown Manhattan, and that Wall Street could be ground zero. I explained that the radius of the fireball varied with the 2/3 power of megatonnage, and that the desk would not give even a microsecond of protection. He agreed, and told me not to tell all this to the other students, as it might frighten them. For that matter, he advised me not to scare the teachers. I did not leave my baby teeth for a "tooth fairy." Rather, I had my Mom snailmail them to someone who was researching Strontium-90 levels in teeth, for fallout research.