There is no official school what's app group (I don't think there is one for any other school?); each class may have a what's app group for communication purposes but I don't think that is for anyone outside that particular class. You can go to KIS facebook page to look for events and activities ongoing at KIS - that is a public page.
It depends on how long you attend the summer class.Full month give the best result. You gain more in spoken english than written english. My son definitely enjoy his summer school classes.