Ranking Students and Get Positions

Good day sirs and mas.

Please. How can one rank students that have scores in various subjects.

Student A. English = 70, Maths= 87, History=57

Student B. English = 60, Maths= 67, History=58

Student C. English = 76, Maths= 88, History=56

Student D. English = 70, Maths= 57, History=97.

I want to  get student the one with the highest average and the average in percentage using codeigniter.

Help me out please.

Thanks