I also went to a school with both Filipino nuns and laypersons teaching English, math, science and everything else in between. Other than a slight accent when I get excited, I think I turned out ok.
My sister went to the International School in Beijing when she was not yet 10 years old. She's doing well also.
Regardless of where your kids go, stay engaged and interested in their progress. The benefits of living abroad temporarily far outweigh the disadvantages.