was taught vs had been taught

Or "was taught by Grandmaster BS Huan in the 60's". It depends on whether the Grandmaster is still teaching or not.

Traditional Taekwon-do is the original Taekwon-do martial art that was taught by Grandmaster BS Huan since the 1960s.

I think "had been taught" should be used instead of "was taught" because "since" is used in the later part of the sentence. Am I correct?

Thanks.

"Was" is simple past tense. "Had been" is past tense referring to a past time. If your point of reference is the present you say "was" or "has been". If your point of reference is a time in the past you say "had been"

" TKD had been taught"... to me, implies that someone else took over his teaching in the interim. I guess that was the case, he retired some time ago, ne?