是否所有IS kinder都要一早報名？

Like the K1 class of KBCK, CNDIS, the reception class of Kellet (probably more), Applications may be accepted from birth, therefore, a waiting list is already building up for the year your child will enter.
For example in KBCK, the earlier you send in the form, the higher chance you get into the morning session.
Like Kellet, they have