Help with ranking

Good day

I am in need of some help with a spreadsheet.

The sheet serves the following purposes:

1) Show list of students and their results per subject.

2) Display the Top 10 learners per subject and grade.

I have created a series of named ranges to make formulas easier.

I have two problems with my Top 10 students.

Problem number one:

I have used the following formulas:

1) =@INDEX(R_Numbers,MATCH(E5,R_Eng,0)) - returns the sequence number of the student.

2) =INDEX(R_Surname,MATCH(B5,R_Numbers,0)) - returns the surname of the student

3) =INDEX(R_Name,MATCH(B5,R_Numbers,0)) - returns the name of the student

4) =LARGE(R_Eng,LEFT(A5,1)) - should return the student's marks for the particular subject (in this case English), in descending order.

The first nine students always display correctly, but the 10th always repeats the first.

Problem number two:

Some students do not take all the subjects. So when I import the marks from the admin system, they will have blanks for subjects with no marks.

The above formulas don't work with these at all, so the Top 10 for those subjects do not work correctly.

I am including an example of the workbook, with dummy data. I would be very grateful for assistance in rectifying these problems. (https://ireneprimaryschool130-my.sharepoint.com/:x:/g/personal/ariddin_ireneprimary_co_za/EQAJv7HaiflEpg8Gjz3yBNsB8p8S25OI7sx_pfOth4QBpA?e=vM0mbx)