Answer: The poem talks about how schoolchildren went through atomic bomb drills during the Cold War.
Explanation: At the beggining, when the character <u>describes his kindergarten school hallway</u>, he shows how the children were lead when there was an atomic bomb drill alert, specially when he mentions the position in which they had to stay ("[...] pressing our heads/between our knees, waiting.") Then, he <u>describes a classmate, Annette, that was probably killed during one of the drills when he says "Why Annette? There's nothing/to be upset about - "</u>, and reflects on <u>what is going to happen because of the war</u>. He realizes that <u>the most dangerous things aren't the bombs, but the war itself, if it keeps going on and on</u>, as he shows in "it is the days, the steady/pounding of days, like gentle rain,/ that will be our undoing."