A study tracking over 26,000 middle school and high school students across a county in central China over 30 months found that while AI use boosted homework scores by 18 per cent and cut homework time from 64 to 45 minutes, it also reduced exam results by 20 per cent. Conducted by scholars from Stockholm University and the University of Hong Kong, the research tracked homework grades, completion times, monthly test scores, and entrance-exam results from September 2022 to June 2025. Around 80 per cent of students reported using generative AI, with Doubao, DeepSeek, ChatGLM, Ernie Bot, and Qwen as the most popular tools. Within six months, monthly exam scores dropped by 20 per cent, and after two years, high-stakes entrance exam results fell sharply, with a 24 per cent drop in the zhongkao high school entrance exam and an 18 per cent drop in the gaokao.