At my school, English is taught by two teachers. These two teachers are not native speakers.
a) At my school, English is taught by two teachers, neither of whom is a native speaker.
b) At my
two teachers (,) who are not native speakers. (correct? Is the comma necessary ?)
c) At my
two teachers, both of whom are not native speakers. (correct? Can we use "both" with negative?)
a and b are fine (I'd use a comma here) - both with a negative doesn't sound too good.