I was picking up my niece yesterday and was early 10 minutes. Got a glimpse of what was happening inside the class. The teacher was using 'hey' and 'hoi' to address the children.
Instead of using 'hey' or 'hoi', I think the teacher could really use other words such as 'anak-anak' or 'murid-murid'.
I wonder where have all the manners gone. And this teacher was not the only one using the 'hey' and hoi', there were others too. It's becoming a standard.