However, I also grade weekly exercise sheets during the semester, and these are committed into a repository, where each student has a folder that... begins with the first letter of their first name. Everyone I have ever worked with acknowledges that you have to shuffle the order in which you grade these submissions each week, for fairness. Several effects come into play: (1) your are usually less tired at the beginning, (2) your mood gets better during the last 2 sheets because you know you are done soon, (3, and crucially) at the beginning, you have not yet seen all the common errors / developed a "feeling" for them, and you might thus miss them in early submissions, but spot them immediately in later submissions.
Another alphabetic effect: In elementary school, my name was on top of the list of students in my class. I remember that I often had to do some special job simply because I was the first name on this list (for example, carry a group ticket when we visited some museum, keep track of something, be the first at something where nobody wanted to be the first, with everyone watching, be the first to be graded in PE, again with everyone watching, etc.). As a fairly shy kid, this already annoyed me in first grade.