There isn't a single "Chelsea School," so admission start dates for Class 9 depend on the specific school you mean, but generally for the 2025-2026 academic year, applications for Chelsea School are often available by September or early January, with most start dates for Class 9 admissions opening around September to January for the following year. To get the exact start date for your desired Chelsea School, you will need to check their specific admissions page or contact the school directly.