Is it unfair to learn?

As I teach my classes, four sections of the same grade level content, I become a better teacher-  I notice the mistakes that the previous class made;  I understand their misunderstandings; I see the gaps in my teaching.  I learn.  That being said, class #4 receives all of my learning from the previous three classes and produces higher quality work.  They may even receive, on average, higher grades (I will check to see if this last item is true).

Is this unfair for class #1?  Is it unfair that the teaching they receive, because they receive it first, will always be a little less complete and polished?  Is this like asking if it is unfair for the first child in a family to have to train the parents?

Now, I return to weave the threads of learning for that first class, perhaps with colors not as bright but beautiful nonetheless.