Wrong. The US has so many school shootings the FBI has no ability to stop them all. The solution of any 'primary' focus is not to concentrate on some safety net authoritarian prevention program. Have you not yet figured out that strategy never works?
The primary focus should be to figure out why there are so many completely disenfranchised youth in the US that are absolutely devoid of life ambition. They feel the only way to make a name for themselves is through murder. It's not that hard to figure out why they do it, often they write it all down for you to read. Read the Colombine guys notes. They are public and they explain precisely what they were thinking.
Blaming the FBI for school shootings is as dumb as blaming homeland security for every murder committed by a Muslim.