def sort_student_score(name_list, score_list):
    """Method that takes a list of names and scores and returns a dict with keys as letter grades and a list of names as as values"""
    score_dict = {}
    for grade in "A B C D F".split():
        score_dict[grade] = []

    for name, score in zip(name_list, score_list):
        if score >= 90:
            score_dict["A"].append(name)
        elif score >= 80:
            score_dict["B"].append(name)
        elif score >= 70:
            score_dict["C"].append(name)
        elif score >= 60:
            score_dict["D"].append(name)
        else:
            score_dict["F"].append(name)
    return score_dict