I have been teaching English for 8 years and I started from a small English academy owned by a Korean. The truth is 'native speakers' can only teach pronunciation and communication. Of course, English schools across Asia prefer 'native English speakers' because Filipinos and even Singaporeans cannot teach American and British pronunciation. Honestly, in my experience, native English speakers are only hired as a marketing strategy, only as a face to attract more students. In reality, they cannot teach grammar to students who are learning English as second language or even as a foreign language. Most students choose Filipino teachers over native English speakers because the former are more creative in delivering classes. They are also dynamic compared to some NES teachers who just depend on their passports. I am not saying all but mostly as a basic observation.