Just let it go. I know it is hard.
My son's school has a "courtesy court." Each month, the teachers pick students in their class who have been courteous to other students and the teachers. At the end of the year, if there has been one or two students who have been outstanding throughout the year, they get the big, year-end courtesy award and a special pin that they get to wear on their uniform throughout their time at the school.
Now accordinding to my son's teachers, he is such a respectful boy, friendly to ALL students, yada, yada, yada. He has never gotten nominated ONCE for the courtesy award. I can also tell you that my goddaughter has been nominated many times and she can be the nastiest thing on wheels--yet she is very smart and is a "teacher's pet" type. So go figure. I let it get to me for a few minutes every now and again, then just let it go.