What method would I need to use in order to prove if Teacher Clarity helped improve my students' post-test scores?

Student Pre-Test Post-Test

1 19 43

2 0 58

3 18 62

4 38 96

5 3 56

6 29 96

7 17 73

8 35 88

9 27 92

10 19 71

11 3 77

12 17 65

13 23 73

14 19 63