Picturing a crowd in its underwear is the worst possible advice to give someone nervous about addressing a classroom full of school children. Still, it’s the advice I received a couple of years ago, right before I spoke at the Priory School in Shrewsbury.

It’s also the advice I chose to ignore this afternoon, when I returned to the same school and to the same children – all grown up, their voices and bra straps having broken under the full force of puberty. With their lip gloss and their lethargy they were almost unrecognisable. And surprising in their intellect.

I was there to teach them about business, but – as per the cliché – they ended up teaching me. One girl told me how she’d secured the rights to all the pin boards in the school and that if anybody wanted to hang a poster they’d have to pay her for the privilege.

“It’s premium ad space,” she said.

“It’s a monopoly.” said another.

The kids were 14!

At that age I didn’t know what was or wasn’t ‘premium ad space’, nor that ‘monopoly’ was anything other than a board game – and a boring one at that.

I guess I was too busy picturing people in their underwear to care. Not much has changed in that respect.