A teacher of English or an English teacher?

[Slam Juice]

I was told once that a person who teaches English as a second language should be called "A teacher of English" but today I came across a phrase "An English teacher" describing the person who teaches English as his second language. Help to clear this up,please!

[vitaly1985]

it doesn't matter.

[Анатолий Д]

"A teacher of English" is unambiguously an individual who teaches the English language.
"English teacher" may have other meanings, e.g. "an English teacher of French and Spanish" means a person of English nationality who teaches other languages.
One more example:
When asked what were her strongest values, an English teacher of maths said...