Assigning value to icon

Is it possible to assign a number value to an icon and then find the average of those? For example, my students get a daily effort grade. 1 is the outstanding, 2 is satisfactory and 3 is needs improvement. I created a quick record setting (like the default attendance one) where I can give a green smiley face for a 1, yellow face for a 2 and a red sad face for a 3. I'd like to be able to then calculated a final effort grade, tranferring these smiley face grades into the format of a 1, 2 or 3. Is this possible?

Yes, you will find the details explained here: Assigning numeric value to icons