You make two important points, and I would also offer one corrective.
First, you wisely point out that at least much more often than not, zero-tolerance programs lead to foolish and even dangerous rigidity, even undermining the very society they were intended to aid.
Second, you point out the the age of the "offender" should be taken into greater consideration. Also seems more than reaonable as we typically do that even when kids use real pistols, not pastries.
The corrective? That the issue is not simply one of addressing physical safety -- at least not in school. Schools are educational settings, and as such, are about nurturing the healthy development of the students, not simply assuring their physical safety. As such, one could reasonable argue that some response was in order here, but something punitive? That just seems wrong. and something as strong as a suspension? That just seems nuts!