My small son is now a K1 student at IMHK where my big son just graduated.
Don't be so scared of the numbers, because they usually seperate the class to 4 groups and every teacher don't look after more than 12 pupils and they have differents rooms/corners of study every day.
They will organize a parent day before start of class and explain how they teach. Actually it is also through play but the kids really learns.
My son is very happy every day, and he cries if we don't let him go to school because he is sick.
As IMHK is an old school, they should have their way. My elder son now is at IMHS and still very happy.
Give it a try. Or ask more at the school, most of their teachers have been working there for a long time.