I tell parents to chill out. And the people. Teachers and Students Personalities are major in high school grades. To sort out student-teacher dynamics, have a teacher conference with Ruby present. Talk about it, together.
Teachers do take the student into consideration.
Find out what matters most in the teacher's grading system. Between You and Me Back at home, confront any real or suspected social issues that can sink grades and prime the anxiety. Kids think they have issues no one has ever had to deal with. I am thinking the worst. Remember, instead, that they really don't have much life experience.