I think their campus has posted the percentage of how many kids go to IS (ESF and others). You can also call them. I don't think they posted that on their website however.
oh............ but that 清潔 ee is shared between two Pre N classes. And the English teacher takes sick leave quite often this year (but another English teacher will take over). PTH teacher is more stable.
So in theory and on paper it is 1:5 for sure (that's why the can charge $7,100!!!!!), but in reality, (in my opinion only), is not.