looping through values

I'm writing a script that does ... stuff, and I found that I'm repeating the same section of code four times, but with two letters changed every time. Is there a way I can condense this into a for-type loop that will loop through a set of values?

So that I can say "do this for each value listed: $grade = FR, $grade = SO, $grade = JR, $grade = SR". Something like that.

Any help would be muchly appreciated.