My son is preparing for the apocalypse but that�s not what�s making me cry

I'M not planning to blub at our sons' primary school leaving ceremony. Sure, one of our boys has been madly practising Green Day's Time Of Your Life to play on his guitar - but that won't get me. I'll focus on the fact that they are ready to move on. Nor am I worried about tear duct eruptions when the boys tip me off about the planned show of photos of the P7 children as babies and the lumbering 12 year olds they are now.

They're growing up - aren't we delighted about that? No more impromptu displays of public nudity. No more being invited into a neighbour's garden for your child to attack their bouncy castle with a sharp stick.

It's wonderful, actually. We don't have to swerve into a lay-by 50 yards from home for someone to stagger out and vomit dramatically at the roadside. As if by magic, the children have stopped posting small pieces of fruit into the car's nooks and crannies for us to discover, months later, when they've turned into a sort of fermenting sludge.

In fact, the boys seem to have decided to manage their own lives, with no interference from us. Every morning we are woken by the alarm one of them has set to go off at 6.30am. It doesn't make a gentle peep-peep noise. It's a terrible blasting sound, as if someone might have tried to gain unauthorised access to a nuclear reactor. Why does he need to be up at this hour? No matter how many times we ask him to change it, it still goes off. Every morning we wake fearing that we should be dashing to an underground bunker.

Even more perplexing, his brother has assembled an "emergency kit" in a rucksack under his bed. Its contents include a torch, compass, pen knife, wire saw, some cutlery and water purification tablets (but no toothbrush), plus a wide array of rations including baked beans and sausages in a pouch designed, its blurb says, to "keep you sustained whatever the extremes". I wonder what extremes he might face in rural South Lanarkshire.

On the front of the emergency kit's sausage ration is the reassuring message: "REAL FOOD READY TO EAT." What else would it be, if it wasn't real? I'm suspicious. You don't see slogans like REAL FOOD READY TO EAT on normal things, like bananas. I read that the food range "can be traced back to the ration packs supplied to the British military on manoeuvres" and it has a best-before date of June 2012. My son hasn't started secondary school yet, but he'll be able to tuck into this "real food" when he's just about to start fourth year.

I start wondering what eventualities he's preparing himself for. Does he know something we don't? Will he share his beans and sausage if the worst happens? Everyone seems grave and earnest at the moment. I thought children were meant to be concerned with having fun, not preparing for disaster. Even my daughter, aged nine, is joining in. "Do you have a pension?" she keeps asking. I tell her that I do, and that it's worth about 3p. "What will you do when you're old?" she wants to know. I don't explain that, with three children, I'm hoping at least one of them will take pity and sling us some cash. Otherwise, why would you go to the bother? Instead, I say that I'll probably have to keep working until I'm 97. Clearly, this doesn't seem right. She is used to seeing grandmas having coffee with friends and doing handicrafts. Not hammering a keyboard and muttering.

She is equally perturbed at her brothers' leaving ceremony. As I sit in the school hall, tears rolling down my cheeks, I see several of her classmates smirking and nudging her. Right now, I'd kill for my son's emergency kit. Bet he has tissues in there.