Crafty lawyers can make the sky green half the time. Even if it were criminalised half of them could probably find some sort of loophole or something.
Again notice your usage of 'reasonable force'. Believe me if a kid is marked, they don't feel 'reasonable force' was used unless the parents were at threat from the minor. I don't know of the NZ equivalents of our own but if a kid is taken to hospital here with unusual marks, bruises, whatever half the time before going to court the cops get called and sometimes if the parents seem responsible the child will be taken by DoCs (the Department of Community Services I think? That or child services or something). Legal peeps get VERY strict with usage of 'reasonable force' and if you have left marks or something it's an assault.
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