My school did it in Y11. That's because in June every year, the exam boards release that year's NEA task and contextual challenges. I'll attach a sample task which resembles the real one that's published every year. You may find some schools do Y10 but I don't think that would be common practice, since a lot of students wouldn't be prepared to decide their final coursework idea in year 9-10 and complete it in year 10; I know for certain I would not have achieved the best grade I could've. If in doubt, just ask your teacher.
My school did it in Y11. That's because in June every year, the exam boards release that year's NEA task and contextual challenges. I'll attach a sample task which resembles the real one that's published every year. You may find some schools do Y10 but I don't think that would be common practice, since a lot of students wouldn't be prepared to decide their final coursework idea in year 9-10 and complete it in year 10; I know for certain I would not have achieved the best grade I could've. If in doubt, just ask your teacher.