I believe a TEFL certificate is invaluable and will certainly help getting a job, not to mention what you will learn that will make you a better teacher.
Also TEFL is recognised the world.
Even someone with a PGCE (post-grad qualification to become a teacher) would benefit from a TEFL because you learn the specifics of teaching English.
You also learn how to handle multi-national classes where you cannot explain anything in the mother tongue, but have to use diagrams and actions to get your message or concept across. For example, learning how to explain verbs using time lines is very useful.
The chances are you'll learn some things about the English language you were only subconsciously aware of, and you look at the language with a view to teaching it, not just knowing it as your native tongue.
So all in all, well worth getting the qualification!
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