I am facing difficult problem regardiing this. My scenario is as follows

" We are in training institude where students of same class are graded by 4 four different instructor. For one instructor , the best student is having maximum marks 70 and lowest is having 55.
For other instructor the best student under his supersivion is having 90 marks and the worst is having 73 marks. So four different instructor give them marks accordiing to their own criteria.
The problem starts at the end of training period when the results of all the four instructors is compiled and final list is made and students are given order of merit. Now over here the students which were with the linear instructor get at the top, whereas the student which might be at top with one instructor will fall some where in middle.
I am also givin example
Instructor A studet marks :- 80, 85 ,78, 75, 88
Instructor A studet marks :- 70, 73, 68, 65 ,60

So if i make overall order of merit all students of instrctor A will get at top which is not true otherwise. How can i solve this issue. is there some thing in stat which can help me