A school in Virginia kicked out a student for a year because he brought a leaf to school from a Japanese maple tree. A school official thought it was marijuana.

The crucial point here is not that the official made a mistake, but that once he knew it was a mistake, he still insisted on punishing the child. This attitude towards mistakes characterizes the most cruel and self-righteous officialdoms. We see it when people are convicted of crimes and then proved innocent: the legal system resists exonerating them. And now, under the guise of "zero tolerance", we see it in schools.

Even if it had been fairly harmless marijuana — or even some dangerous poison — that would be no reason to punish the child for it in such a harsh way. A reprimand ought to be enough.