Andrew Pollack calls the Parkland, Fla., school shooting “the most avoidable mass murder in American history.” Avoidable because of how the system refused to react rationally to years of warning signs about Nikolas Cruz. And the book Pollack, whose teen daughter was one of Cruz’s victims, has written with Max Eden shows that the same failure could occur almost anywhere in America. Excerpted in Monday’s Post, “Why Meadow Died” reveals educational records, like teacher daily diaries, tracking Cruz’s flagrantly psychotic behavior from an early age.