I'm a non-native speaker who has been teaching in China for almost 4 years and presently teaching in an international school. In my whole time of teaching here in China, I've had many native speaker co-teachers. And I can say that based from my experience alone, I've never met a native speaker who can teach very well here in China(no offence to some nativespeakers who can teach well).I used to work in another school with 8 foreign teachers(6 are native speakers and 2 are non-native speakers and I'm one of those). Those six native speakers were not given a chance to sign for another contract for the second semester because the school wasn't impressed with their teaching. Some of them swear in class, can't spell, etc. I think the main reason for those teachers for losing their job is simply because they are not teachers. They are just high school graduates who are hired as teachers because they're white. Sadly, this is how it is in China. But some schools are changing. There are still some schools who look for the teacher's teaching skills and not his color.