Formatting data in a CSV file (calculating average) in python

import csv
with open('Class1scores.csv') as inf:
    for line in inf:
        parts = line.split() 
        if len(parts) > 1:   
            print (parts[4])   


f = open('Class1scores.csv')
csv_f = csv.reader(f)
newlist = []
for row in csv_f:

    row[1] = int(row[1])
    row[2] = int(row[2])
    row[3] = int(row[3])

    maximum = max(row[1:3])
    row.append(maximum)
    average = round(sum(row[1:3])/3)
    row.append(average)
    newlist.append(row[0:4])

averageScore = [[x[3], x[0]] for x in newlist]
print('\nStudents Average Scores From Highest to Lowest\n')

Here the code is meant to read the CSV file and in the first three rows (row 0 being the users name) it should add all the three scores and divide by three but it doesn't calculate a proper average, it just takes the score from the last column.