Could someone mabye find why the code is not working?

```
grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]
def print_grades(grades_input):
for grade in grades_input:
print grade
def grades_sum(scores):
total = 0
for score in scores:
total += score
return total
def grades_average(grades_input):
sum_of_grades = grades_sum(grades_input)
average = sum_of_grades / float(len(grades_input))
return average
def grades_variance(scores):
average = grades_average(scores)
variance = 0
for score in scores:
variance += (average - score) ** 2
variance /= float(len(scores))
return variance
```

Thats the error message: grades_variance([8, 3, 9, 3, 5, 5]) returned 1.0416666667 instead of the expected: 5.25