A reward for top students

In each class, there are 1 or 2 students that I excuse from the final exam and give an A+. I base it on the following criteria:

1. Grades (must be in the top 3 in the class).
2. Attendance (must be perfect).
3. Homework (must have done all of it).
4. Attitude (must be cooperative and enthusiastic in class).

I don't tell my classes of this possibility during the semester, they only find out on the last day of class when I tell the one or two students. I do this as a way to reward the students who are just good students without any obvious motivation. And it's also easier on me, as I have about 15 less students that I need to administer tests to and these students would get an A+ anyway. Works for me, works for them!