I am challenged with this problem as well, both the underachiever student that isn't doing the work, and the student with low academic skills.  The underachiever I try to encourage them to want the good grades.  The student that doesn't have the basic skills  I will put more effort into leading these students to resources to get the remedial help they need to succeed. 

I try revive the dream of why they are there, I believe they all have the potential to succeed... it is fully dependent on how much time and effort they are willing to invest in that… >>>