The pre- and post-test are identical. They include 40 multiple-choice problems. The grades of both tests are out of 40. The y-axis of the first two graphs are percentages of students who've got the specific score. 

As shown in the above figures, the overall grade (peak value) changes from 50% to 60%, math part grade (peak value) changes from 65% to 75%, and physics part grade (peak value) changes from below 40% to 55%. A significant progress can be seen.