If teachers add any lasting value to a student's existence, it probably won't be in the form of an elevated test score. It will be in the form of opening the eyes of a student to look more deeply (both within and at the surrounding world) and see things in new ways. It will be in the form of recognizing that goals in life are not standard issue. It will be in trying to give someone the tools in life to reach his or her individual goals--even if it only means restoring a faith in himself, or herself, or in humanity.
If I add any value to a student's life, it will not so much be in the form of teaching to standardized test answers as teaching students to question. The lasting value of education lies in empowering individuals to keep asking the questions that move them ahead--no matter what direction it leads--long after all teachers and any tests have exited the scene. The lasting value lies in a concern for the whole child. I don't buy into grit (which sometimes implies little more than suffering through hardships which others bring upon you) as much as I buy into promoting the joy that can help individuals find some security and satisfaction in charting their own courses in life.