Non-native speaking teachers are a clear example and motivator for their students. It’s encouraging for a student who is struggling to learn a new language to be taught by someone who has been there and done it. Non-native speakers are also brilliantly able to model and share the skills / strategies they used to find success.
Studies also suggest that the teaching style typically deployed by non-native teachers may also be more effective than their native-speaking colleagues. They deliberately seek to integrate language into situational contexts to provide real-life relevance for students, whilst native speakers tend to teach using “more abstract” principles.
As outlined above, and of particular importance to lower ability students, teachers that share a mother tongue with the student are well-placed to teach effectively. They are able to use their common language to explain / translate difficult concepts or more easily teach key vocabulary. Knowledge of the students’ background also helps non-native speakers to better understand prevalent local teaching / learning styles / techniques as well as national policy and qualification frameworks.