26,000-Student Study Reveals AI's Hidden Cost: Better Homework, 24% Worse Exam Scores
A new study of 26,000 Chinese secondary school students reveals that AI use improves homework scores by 18% while reducing exam scores by 20-24%, with the full effect taking two years to surface.
A major study of 26,000 secondary school students in central China has revealed the hidden cost of AI use in education. Researchers collected 30 months of panel data tracking monthly exams, homework scores and completion times, and high-stakes entrance exams.
Key Findings
Six months after first using AI, homework scores rose by 18% while completion time dropped from 64 to 45 minutes. But closed-book exam scores fell by 20%.
Two-Year Delay Effect
The full negative impact on high-stakes entrance exams took about two years to surface, ranging from an 18 to 24 percent decline. Short-term studies therefore miss the long-term cost to learning.
81% Show Signs of Outsourcing
After more than five months of AI use, about 81% of students finished homework in under 50 minutes — faster than even the quickest non-users. The combination of short completion times and high homework grades suggests outsourcing.
Conclusion
The study reveals AI as a double-edged sword in education — improving efficiency while undermining genuine learning. Short-term gains mask long-term costs.