You should be fine. We didn't apply for my daughter until she was 15 months old and we were able to get in to the Upper Kindergarten class when she was 3 years old (lower kindergarten starts at 2.5 years). There aren't any assessments for acceptance into Thomas's Kindergarten; it's simply done by the waiting list (the assessments don't happen until primary school). However, you must apply separately for the primary school and those lists fill up VERY quickly, so I would apply ASAP if you want to get on the list at Thomas's Battersea, Clapham, etc. Attendance at Thomas's Kindergarten doesn't guarantee acceptance into their primary schools, but it does guarantee you an assessment. Best of luck!