Customize ERPNext Schools grading system

Hi everyone,
I’m from north Africa (Algeria), i’m new to ERPNext, here we have the same educational system as France grades are numeric from 0 to 20, 20 being the best grade, 10 average, 0 the worst, i’d like to know if it is possible for me to customize schools module assessment grading scale so that it fits the french grading system?
has anyone already done it?