score_list = [65, 92, 78, 90, 45, 83, 57, 96]
score_dict = {
    'high': [],
    'middle': [],
    'low': []
}
for score in score_list:
    if score >= 90:
        score_dict['high'].append(score)
    elif score >= 60:
        score_dict['middle'].append(score)
    else:
        score_dict['low'].append(score)
print(score_dict)