Please help with while loop in C

#include <stdio.h>
#include <stdlib.h>

int main()
{
    char grade;
    float gradeScore;
    int numberClasses;
    int n;
    float score;
    n=0;
    gradeScore=0;
    numberClasses=0;
    printf("How many classes are you taking (MAX of 8)?");
    scanf("%d",&numberClasses);

    while(n<numberClasses){
        printf("Please enter your letter grade in  class:");
        scanf("%s",&grade);
        if(grade='a'){
            gradeScore=4.0;
        }else if(grade='b'){
            gradeScore=3.0;
        }else if(grade='c'){
            gradeScore=2.0;
        }else if(grade='d'){
            gradeScore=1.0;
        }else{
            gradeScore=0.0;
        }
        return gradeScore;
        n=n+1;
    }

    return 0;
}