"Sir, if you were to suddenly appear in space would you be able to talk because you already had air in your lungs?"

This was a question shouted out by a year 8 pupil last week in the middle of a class discussion about breathing. How would you answer? Perhaps with "That isn't relevant to what we're learning about today, ask me again later"? Or would you take a huge detour and try to explain what sound is and how your body would react in space? The question itself was so unrelated to the topic we were discussing that it might give you cause to wonder whether the pupil had been paying any attention at all, so perhaps you would give them a warning for being disruptive and tell them to not shout out in future? Perhaps the question was actually a really good question and the pupil had just made a link between breathing, the fact that space is a vacuum and that sound can only travel through a medium? Did that child just have a major conceptual breakthrough or was the question a sign that they had switched off and weren't listening?

I had to make a split second decision about how to respond, was it a good question or was that pupil being a distraction? I needed more information.

"What makes you think that?" - Me

"Well, in space you can't talk because there isn't any air is there? And sound needs air doesn't it? So if you took air with you, you would be able to talk right?" - Pupil

Aha, so it was a good question then! At which point another pupil joined in:

"But you would blow up in space!" - Pupil 2

"Yeah, all your blood would come out your eyes" - Pupil 3

"That's disgusting!" - Pupil 4

Now we are really off topic. I'm happy that the first question was actually based on some pretty reasonable thinking by that pupil, but the conversation is at risk of losing any value, so I said this:

"It is isn't it! But did you know that if you were to breathe out before you 'appeared' in space you could probably survive for about 30 seconds with no long term health issues!" - Me _{[This was based on what I could remember from having read this article, apparently it's closer to 90 seconds that you could survive without a space suit!]}

"Is that because you wouldn't have any air to rush out?" - Pupil 2

"Yes! Or at least not as much! Holding your breath is a very bad idea! So what about talking?" - Me

...

The rest of this conversation lasted for a couple of minutes before we eventually got back on task and I set them working on the next activity. Was it a wasted few minutes? Did they learn anything? Did I learning anything? This kind of reflection is a vital part of being a teacher, continually assessing your own split second decisions after the fact. Did I make the right decision following up with that question? Should I have stopped the conversation earlier? Should I have gone even further and tried to involve the rest of the class in the debate? It certainly didn't help the class meet the learning objective for the lesson ('To be able to explain why animals need to breathe') but it did give me some insight into how a few of the class were making links between different areas of science.

I'm not afraid to go 'off plan' in my lessons, if I can see a way to get a point across that I hadn't previously thought about I will take it just to see what happens. This kind of risk taking is what can make one lesson go spectacularly well and the next lesson go spectacularly badly! Knowing when to pull the plug on an idea is an important, and difficult, skill - especially when it means admitting to your pupils that you have messed up and that your lesson plan hasn't worked! One advantage of this 'risk taking' in lessons is that, good or bad, it always gives me plenty of thoughts to reflect on and thus learn from!