Because you need to have the exact score of ten on your test for each teacher if one in 9 or below it won't work but if you used cheats to make your score above 10 it also won't work so retake the test until you get a 10 or use the cheat options to make them 10
P.S. i will not tell you how to use cheats if you don't know & if you do just use them its easier.