Hey there, I was also trained in grade school, and in 8th grade, our history teacher spent a week on surviving a nuke.
Included using a Geiger counter, and demonstrations on how to peel a radiated banana to make sure it was safe to eat.
As long as you are at least 25 miles from ground zero and have shelter and 2 weeks of food and water, survival is very possible. After 2 weeks limited trips outdoors to re supply are ok.
These days they give them active shooter training. Just about as useful as the under the desk training was, I’m sure.