Hi mummy, each kumon centre really depends on the centre you register your child in. The concept of kumon is to train a child's ability to be an independent learner. Regarding the duration of each session, it really depends on your child's learning pace, as some who finish fast is because they've build up the speed and accuracy, while the others who take more time could be because of the corrections they have or that they could be learning something ahead of their school level. Idk if this applies to all centres, but for the centre I worked in previously, if a student finishes before 30 mins, we would usually give them their homework corrections to do. Hope this helps