There is no such "best jungle warfare school" and there is a very simple and logical reason for that.
Jungles or forests differ from region to region in temperature, climate, flora, fauna, soil composition, humidity and a host of other things. People used to fighting in the jungles of SEA will find the jungles of Africa and South America as alien; the same goes for the people of Africa and South America.
In South America you have jungles where there are frogs so toxic that contact with human skin can prove dangerous.
What the writer here means to say the CIJW is a good institution and one of the leading ones in the world.