Try to motivate him to try his best in the next exam. be beside him and do anyone talk about matks and exams until he feels better. try to explain him where he is behind.
1) we could help her for her practices
2) help her out in her notes and if she faces any problem in her homeworks.
3) make her believe that we are always for her help
4) try to comfort her by telling that their still a lot of opportunities lleft to prove herself so should not be disheartened by this particular result