To his credit, Preston pulled himself together. He gave the whole pitch. The slides. The numbers. Teachers optional. He skipped that slide quite quickly.

When he'd finished, I asked my questions.

“What happens when a child gets the answer wrong?”

“They don't,” said Preston. “The app gives them the right answer.”

“So how do you know they've learned anything?”

“They finish their homework. Parents are happy. Kids are happy.”

“But can they do it on a test? Without the app?”

He hesitated. “We're still collecting that data.”

“And when a kid is stuck and frustrated and wants to give up, who sits beside them?”

He opened his mouth. Then he closed it.

I nodded at the screen.

“Could you play the demo again, please? The fractions one.”

His co-founder pressed play.

The little video popped up.

“Okay, so here's the trick with fractions. Imagine you've got a pizza…”

I let it play for ten seconds. Then I spoke, at the same time as the recording. Word for word.

“…and you've got to share it fairly with three friends. How many slices does everyone get?” Preston stared at me. Then at the screen.

The co-founder slowly took his hands off the laptop.