i think you can try ISF, they emphasis they are not an international school becasue they stress on PTH chinese a lot. 70% on chinese / 30% on english.
If english foundation no good, I think you can forget SIS ( sorry to say but this is the true). As I know enen PY1 kids in SIS, all of them can speak in english freely . Their parent want them to learn more chinese in SIS.