How to prevent students from having an unfair advantage on exams, when they are held on different days? I teach a writing course to different sections, across different days of the week. From the schedule, some students will take their mid-term exam early in the week, while others will take it later in the week. Recently, I found one student who was “just checking to see what the exam was like”, but was planning to go to another session to actually take the test. I realized there might be a variety of ways that students taking the exams on Friday would have an advantage over those taking it on a Monday.

I've taken the following steps in an attempt to address this problem:


I build multiple tests, e.g. "A", "B", "C", etc., which are of similar difficulty, have the same types of problems, but different subjects. "A" is given to one section, "B" to another, etc.
Provided a sample test that students can print and practice with and discuss with me in class.


Note that, there are several challenges to administering this:


The classes are large, and the school offers me no assistance in managing the exams.
Many students regularly attend my lectures during sections that they did not register for, so I will not easily recognize who belongs in which time.


Are there any additional steps I should consider to make sure the test is administered fairly?
There are various ways of preventing students from showing up on the wrong day or showing up more than once. The first step would just be to tell them straightforwardly that it's not allowed. You could also assign seats for the exam. Assigning seats has the added benefit of reducing opportunities for copying from a neighbor's paper; they can't just choose to sit next to a friend or sit next to someone they know is doing much better in the class.


  I teach a writing course [...] The classes are large, and the school offers me no assistance in managing the exams.


The enrollment of writing classes taught by a single instructor is usually limited because it's not practical for the instructor to grade large amounts of written work from a large number of students. At some schools, writing classes are large, but there are TAs who read papers. If you're a single instructor teaching a writing class to a large number of students, then that's a problem in and of itself; these issues with exam arrangements would then be a symptom of the more general problem.