That sounds like a universal experience to be honest; a lot of English teachers (that aren't native English themselves) often over-estimate their own abilities.
And not just restricted to English; it's a very common experience in the U.S. for native speakers of, e.g. Spanish, to end up in Spanish-language courses with non-native Spanish teachers, with modest Spanish skills. I assume it's the case with all language teachers especially at a non-advanced level.