A 30-month study of 26,000 students finds AI's learning cost surfaces only after two years
A panel study of 26,000 Chinese secondary students found AI use cut homework time from 64 to 45 minutes and lifted homework scores 18%, yet monthly exam scores fell 20% within six months and entrance-exam scores dropped 18-24% after two years. The loss concentrated in students who outsourced the work — fast finishers with high homework grades but low exam scores — and stayed invisible until the two-year mark, meaning shorter studies systematically understate it. The effect scaled with dose: an hour of weekly AI use cost about 5%, five hours or more cost 30%.
Source: the-decoder.com ↗
Six months after first using AI, homework scores rose by 18 percent while average time per assignment fell from 64 to 45 minutes. At the same time, scores on monthly closed-book exams dropped by 20 percent.
Why this matters
- → AI homework help masks learning collapse that only emerges after two years.
- → Short-term studies systematically underestimate damage; entrance exam scores dropped 18-24%.
- → Effect concentrates in students who outsource work, making it invisible to teachers.