Recall that Dusco Popov, the allies double agent in WWII, told J. Edgar Hoover in the summer of 1941 that the Japanese were planning to bomb Pearl Harbor. Hoover chose to ignore the warning, as Popov, the real person on whom the James Bond character was based, was a renowned playboy whose morals Hoover abhorred. So, missing what in hindsight is a crucial clue that can avoid a tragedy is nothing new.
I suspect that all types of law enforcement agencies get thousands of leads that prove to be worthless deadends. However, if law enforcement is so underfunded as to be unable to follow crucial leads and enforce existing laws, or waste resources going after low profile offenders, then we’ve got a problem. One would think that a lead regarding a potential school shooting, a clear act of domestic terrorism, would be of the highest priority.