Using generative AI for schoolwork can boost homework grades and save time, but significantly impairs students' actual learning and long-term exam performance. Is there an optimal amount of AI exposure? Takeaway: This study investigates how students' real-world, self-directed use of generative AI affects both their day-to-day homework performance and their performance on short- and long-term exams. Key Points Productivity vs. Learning: Generative AI boosts students' homework