of course they wouldn't understand if its not in their language. you would need to sign to them in their native language for them to understand. if included common gestures in ther languae mixed in with ASL it wouldnt make any sense to them.
They wouldn't understand the words as simple as that like I've been attempting to learn a Philippino language and its hard to learn some of the words because sometimes when the words are used in a phrase it sometimes modifies the words so even if they understood the core language the phrase might change the words and throw them off
the purpose is to get the teachers to stop using red pens because it is effecting the way the students feel, because the color red usually symbolizes anger and bad things, so it doesn't make the students feel good.