'As' has no tense: only finite verbs have tense. Yours is in fact not a grammatical sentence; the closest approximation would be 'he is like a teacher', in which 'like' is a preposition, and the prepositional phrase 'like a teacher' is an adverb of manner. 'Being' in your sentence has no tense either; it is a nonfinite '-ing' verb form used as a noun and is called a gerund.
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