World's biggest school test asked 15-year-olds how they use chatbots. Where the machine wrote the essay, scores fell — unless lessons taught them to check it.

Two-thirds of Singapore's 15-year-olds use AI chatbots to help them learn at least once a week, far above the 46% average across OECD countries, according to Programme for…

But using AI almost everyday can create a negative feedback loop.