How many students and parents don't recognize they are in trouble until students get to high school? By then only massive effort by the student and his or her parents can have a chance of saving the student's educational life. People more often give up then than try.
Teachers often see unteachable students before anyone else. Unteachability in my mind is not permanent if it is addressed sincerely. Unteachability may be from non-effort, emotional baggage from home life, and/or deficient background skills for the current work. From middle school on, no single teacher can fix any combination of these problems. A teacher can do the most by being free to point out unteachable students. Teachers are severely criticized today if they initiate such a discussion. I would suggest that parents and school administrators encourage such discussions.
Perhaps there needs to be a well understood coarse of action to address student unteachability upon first recognition. I would guess that the caring effort by all will require more emotional strength and tangible resources than we currently believe.
If I am right, can you go there?