Strange, as a regular traveller in SW London, I was well aware that this schoolboy would have to pay full fare, and had my YP form ready for the evil day.I wouldn't expect a school girl to think she has to buy an adult ticket!
NOT a dig at the OPs daughter, as there wasn't a scheme that blurred the lines between adult & child, nor did I have to worry much then about administrative boundaries.
I'm with those who think that, based on whats been reported, the treatment has been ueavy handed but legally correct. I would just hope that those taking a strict liability line remember that just because the law says something, that does not make enforcement of the law just.