and why isn't it efficient?

I really like this solution. It doesn't draw on any external utilities and it is really thinking 'outside the box'. Just because the problem defines the input as number, doesn't mean it has to be processed as a number.

I like the way your mind works!

I think you do make a good point. What you say makes sense. However, in looking at the test cases, it appears that 'your_points' are not included in the 'test_scores' and that 'class_size' matches the number of provided 'test_scores'. So, mathamatically, to get the most accurate result, you would have to add 'your_points' to the array of 'test_scores' and then increase 'class_size' by one. However, doing this will not change the outcome of the final comparison of class average to 'your_points'. Adding you score will bring the class average closer to your score, but cannot cause the average to move above or below your score.

I guess it pays to be familiar with all the functions and methods python makes available. Which is why I am doing these exercises - to learn. And, failure is such a good teacher.

Perfect choice in variable names. No comments needed. Love it!