It's not clear what is meant, but presumably you'd teach EFL in England, as opposed to French or German to English kids.
For one thing, teaching French to British children is more of an uphill battle; there is little French in their lives, so they harly ever feel it's relevant to them, unless you make it fun.
Teaching EFL in England, the immigrant kids are dying to learn, to overcome the difference, and it's relevant to their lives. You can take advantage of all the English they can use in England.
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