On the edge of being accepted? It's been part of standard English for over 500 years!
Read into that what you will, but perhaps you're just trying too hard to take offence.
There has been cases of 17-year-old minors raping and killing that went completely free (or spent a few months in juvie).
What I'm saying with this is that yes, I agree with you: The age of the perp should be considered. But we should also consider the crime in question.
In this case, both age and 'crime' account for what is just a prank with no harm done (apart from bruising some teacher's ego). Even expelling the child would seem to me a bit excessive, but I could understand the school doing that. Anything more is just disproportionate.
Am I the only one who thinks parents should be held criminally responsible for not training their kids properly? It makes sense, doesn't it? If the child isn't considered responsible, then the person responsible for the child should be.
Did you participate in that candle march?
Lets not be careful at all at uploading some basic truths - minors are minors and we _adults_ can't change the definition based on our communal level of outrage.
The incident I mention, by the way, happened a few years ago and it was a group of high schoolers, all of them minors (except one, whose 18th birthday had happened a few months before, he was the only one charged as an adult).