When the teacher asked what "symmetry" was, the boy thought for a while, then replied, "Is it where they bury dead people?" Similarly, one key stage 2 pupil thought "transparent" was "when a boy wants to turn into a girl".
Every week examples of these kinds of misunderstandings are sent in by teachers to the "Overheard" column in TES. Sometimes they are cute, often they are amusing.
But they don't exactly bode well for peer learning, the subject of our special report this week. If you put the pupils in charge of teaching each other, what kinds of misconceptions will multiply?
As Professor Keith Topping, one of the UK's foremost experts on peer learning, says: "One of the worries with collaborative learning is that you can end up with the blind leading the blind. You can get one supremely confident pupil in the group who leads the others on a wild goose chase, which takes everyone down the wrong path."
Yet, despite this danger, the overwhelming international evidence shows that peer learning is extremely effective. Giving up control to the pupils may feel like a risk, but done in the right way, it pays off in spades.
Many secondary schools may think, "Well, we do it already". And it is true that a lot will have buddy schemes and peer-mentoring for literacy in place. But the classic approach of getting sixth-formers to help coach Year 7s and 8s may not be the one that works best - even if it does have its own benefits. Perhaps surprisingly, it turns out that peer learning makes the biggest impact within primary schools.
But what about the risk of misinformation spreading? Well, pupils can also be very good at correcting each other. Earlier this year, a teacher sent in to the "Overheard" column this conversation between two pupils taking part in a peer-marking exercise.
Joe: "Erm, I think you got this bit wrong, Sam."
Sam: "Looks OK to me - what's wrong with it?"
Joe: "Well, diabetics don't really need insulation, do they?"