Another snip> from
FindLaw's California Court of Appeal case and opinions.
“[A] parent may be guilty of contributory negligence in not giving proper supervision over a child, but ․
it is a question of fact for the jury to decide whether such lack of supervision was negligence under all the circumstances.” (Christiana v. Rattaro (1947) 81 Cal.App.2d 597, 599; Baker, supra, 73 F.2d at p. 828
Here is, IMO, a court opinion stating that conduct that might be considered negligence in one situation, might not be considered to be negligence in another situation.
Now I think I know why the subject of banging on glass at the hockey rink is pertinent to this case. Is the act of allowing a child to bang on glass, in and of itself, negligent?