My daughters attend classes from Gifted Sg. The school only accepts students who are gifted. Very low class teacher:students ratio.
Teachers are specially selected. Heard they are current or former GEP teachers, most of the teachers(if not all) are gifted as well.

They have a tutor for English+Maths, a tutor for Chinese and attends weekly Chinese class at Berries.

In addition to the above, they are currently doing piano, hip hop, tennis and swimming. Currently trialing Stanford's Gifted and Talented online Mathematics course.

For this school holiday, they will be doing a crash course in English Chess.