Serendipity sometimes strikes my planning. In a week when every news bulletin is screaming ever more dramatically about obesity, we are starting a unit on "Eat more fruit and vegetables". Can anyone suggest why the Government might want us to eat more? "Obesity!" shouts one of the chubbiest Year 6 girls.
"More?" I'm hoping for a sentence, perhaps to widen things a little.
"Fat!" Ah bless. Does dear Ayo think I`m unsure of the word? No, he's staring nastily at Delivan, who suffers from a syndrome that causes accelerated growth and premature greying. I knew this was going to be difficult.
I move on to the subject of poo, well, fibre to you and me. Rather than the expected over-excitement and general bad taste, the boys all seem to be studying the floor. Does the male obsession with the bowel and extended toileting requirements really start this early?
We move on to how many portions of fruit and vegetables we ate the day before. A range of peculiar answers is thrown at me - beef curry, Weetabix; some laughably understandable - peach yoghurt (well I doubt it actually had any bits in it, anyone under 14 hates bits with a passion), strawberry ice-cream. Then Marcus, who has been rolling his eyes in derision, announces "chips and crisps". It makes me look like a paragon of virtue: vegetable soup for lunch and salad for dinner, a whole two portions. Never mind that I can't remember the last time I looked a piece of fruit in the face, and shun water in favour of coffee, coffee, coffee until I'm wheeeed-up to the ceiling. At least it gives us a meeting place.
All the foods they're most keen on seemed to be referred to by brand name, so the answer is obvious. Hand over to the woman from Sainsbury's. Pat guides us on a fact-finding mission through fresh produce, where the butternut squash draws a fascinated crowd - "looks like an elephant poo" - and Ayo stares in disbelief at a pomerino. "It's made up, innit?" I catch David fondling the coconuts and can't help taking a picture for the staffroom.
Once we move into the aisles to do canned foods, juices and frozen - what Delivan describes with obvious relief as "real food" - the class becomes glazed, seemingly hypnotised by anything containing sugar or recognisable from an advert. Just looking at the packaging has the effect of a full-on, we're-going-on - a-trip packed lunch, so by the time we get to tasting they are as high as kites while I am in need of a caffeine hit.
On the walk back, the air is thick with brand names. Every one can recite the jingle: "Eat 5, stay alive", but until fruit and vegetables are branded, put in bright packages, overpriced and advertised to death, there's no hope. "Vegetables? Yeah, we did them in Year 6."
Mandy Starnes teaches at Bessemer Grange primary school, London borough of Southwark