This is a 'how long is a piece of string' question, but here goes!
Had a spouse that was Oz trained and she taught for 3 years at an international school in HKG. Standards same as average private school in oz. Two major differences...ESF(and some international schools) are based on pommy system so you will find your child/ren doing class/es a year or so ahead of back home. We held our child back so that she was the oldest in class rather than youngest...she had no problems fitting in back home in the same school year. Mind you she got her intelligence from the non pilot half!
The other major thing...sport/grounds/nature. There is nothing you can do about that whilst you chase the almighty dollar and work in HKG. Whilst they are young DB is ok...once they get to teenage levels it may be a problem!