Is the sentence:
He is, or at the very least, is among, the tallest in our school.
grammatically correct? Note that (I believe) that this parallelly states that "either he is the tallest [person] in our school or he is among the tallest [people] in our school." However, the parallelism doesn't work all the way, as in the first part, "tallest" implies "tallest person" while in the second part, the same word is used to imply or mean "tallest people". My question is, is this alright?