Homeschooling + local school classes if you can afford the time.
Most countries offer a high school equivalency course (or rather year by year k-12) complete with study guides and teacher’s guide for homeschooling.
You’ll need to take certain exams with local qualified notary or officials (for supervision) and send them home for evaluation but you’ll probably have better control over what trash goes into your kid’s brains (they can do that easily themselves without a rich expat high school thank you).
Several of the local school offer “exemplary classes” that allow foreign participations.
It’ll round off your kid and make them know that they are not really living in China… but a small bubble resembling China as expat kids (well, replacing it with a bigger bubble that, while is very close to China, is essentially filled with middle-class Chinese).
It would also likely not make them into the typical “expat brats”.
For expat friends, there are plenty of children’s activities for expats only… sports is a great option.
Some from personal experience, some from listening to others, but I believe in it. Also, it’d be much cheaper this way… again provided you have the time to homeschool.