You try to consider St. Margart, Tsung Tsin Primary School ( international section ) or Po Leung Kuk Choi Kai Yun. They are same as International school, but the school fee are not so expensive. Also, they have many foreigner teacher! Fluent English in all classes, except Chinese.
http://www.cky.edu.hk/
here is the website. But it is not a IS, I think. They do have lots of English speaking teachers. I heard they have good results on both chinese and english subjects but the entrance screening is very competitive and pupils there have to work very hard too.