You have to use if
and else if
, because if the first condition doesn't match it will exit and will not reach the nested (the other) conditions:
Try to change it like:
if (score >= 90) {
System.out.println("Your score is " + score + " which is an A");
} else if (score >= 80){
System.out.println("Your score is " + score + " which is an B");
}//and so on