In my thinking the two largest international schools are WAB and ISB. Both are private non-profit community schools and are located in the Shunyi suburbs. ISB is the main American school while WAB has a greater mix of nationalities.
Thanks for the recommendations Barker Hicks! We actually just completed a post on Expat Quotes about International Schools in Beijing. There are many, many schools in Beijing, let alone China! It's great to get some personal feedback from an expat in China. Welcome to EasyExpat