He won, which could then be said to "prove" the vision.
Scoffing is easy in an age of scoffing, as older students can appreciate.
Students need to understand that some people believe that images such as these could be supernatural signs. Famously there was an Indian bread bun revered because it seemed to have Mother Teresa's - soon to be Saint Teresa's - face on it. Hilarious to scoffers; reverential to the convinced.
But it is important to remind students that the majority of religious believers would be unlikely to accept these images as signs from God. Such images provide easy ammunition for rationalists to present religious people as stupid or gullible, because it is always easy to come up with scientific explanations - or, at least, coincidence. But their faith is real.
Older students can appreciate that these visions do not create faith but may strengthen or confirm it: the same is true of scepticism. Classes can discuss this and pore over the pictures with relish. The task for the RE teacher is to deal with the evidence and assumptions part of the debate while reminding students that religion often lies in the domain of the emotions and experience. How might they feel if they had been present when this phenomenon was seen? Or if a close personal friend or family member had experienced it? Is seeing always disbelieving?