It's Friday, and if your house is anything like the ones around me, back-to-school season is fully underway. New backpacks, new schedules, and for a lot of families, a new question nobody quite has an answer to yet: what do we do about AI and homework?

There's a new study out of Stockholm University and the University of Hong Kong that's actually useful here. Researchers tracked 27,000 Chinese students, ages 12 to 18, over two years. About 80% used AI models like Doubao and DeepSeek for schoolwork. The other 20% didn't, and became the control group. It was covered by the Economist this week.

The AI users saw their homework scores jump 18%, and finished assignments almost 20 minutes faster. Sounds like a win. Except on their monthly exams, those same students scored 20% worse than the kids who did homework the old-fashioned way.

Homework used to predict exam performance. Now it's nearly the opposite. The kids with the shiniest homework scores are often the ones who get hit hardest when it counts.

And the penalty wasn't spread evenly. It concentrated almost entirely among students who rushed, who used AI to get the assignment off their plate fast. Students who used AI but still put in real time, treating it like a tutor that explained a concept rather than a machine that spat out an answer, barely lost any ground.

So if you've got a kid heading back to a desk this month, a few concrete things worth trying:

• Answer first, AI second. Have them attempt the problem on their own, even badly, before opening the chat. AI should check or clarify, not originate.
• Make them explain it back. Close the laptop and ask them to walk you through how they got the answer. If they can't, they borrowed the answer, they didn't learn it.
• Ask "why," not "what." Instead of "what's the answer," the better prompt is "explain this like I'm confused" or "what am I missing here." That's the tutor mode that held up in the study.
• Watch the clock, not just the grade. A homework assignment finished suspiciously fast is worth a look, even if the score is perfect.

And if you're not a parent, or your kids are grown, this still applies to you. Swap "homework" for whatever you produce with AI at work: the deck, the memo, the proposal. The same test holds. Could you explain it back without the tool open? If not, you got the homework score and you're about to sit the exam.

Have a good weekend.

Alex