The awful conundrum is that of the responsible child vs. the irresponsible, dangerous or suicidal.
I could cite examples of each. Hopefully parents have insight into their children. The bad things happen when they don't.
There is no general answer - as a parent you need to decide.
Society seems to be more concerned with the risks from the bad situations as compared to positive self-defense benefits.
However, that is part of the general debate over guns in the USA.
I will say that as a caution, the parent who says they rule with an iron hand, sometimes are clueless about what actually is up with their kids. Similarly, the overly permissive can be clueless as to risks. Honest involvement is needed.