on testing...alone or in groups

I have the debate each semester as to how to administer speaking tests: alone in my office or in groups.  This year, I chose groups of 4, while the other students wait outside the classroom for the following reasons:

1. One of my co-workers got accused of sexual abuse last year and I want to avoid having a student in my office, alone, ever.

2. I want to avoid the illusion of having favorites.  If there are 3 witnesses to a speaking test, then students probably won't appeal their score.  When someone gets 3/15, it should be obvious to everyone in the room why.  Same with the student who gets the perfect score.  When students are alone, they have nobody to compare themselves to and the poor students have a tendency to think that they're better than they actually are.

3. It goes quickly.  I can do 25 students in just over an hour.  If they come individually, most of my time is taken up going back and forth to the door to call in the next student. 

4. It's easier to fail the poor students.  I have a harder time doing it when students are alone, since they are not so afraid to appeal/show their emotion when they're alone.  When there are 3 other people in the room, they are more embarrassed to do this and will usually just leave the classroom without some sort of sad story. 

5. And finally, the students don't seem to be so nervous when they're together.  They like having their friends there and since Korea is all about the group they don't seem to mind doing the test in front of their classmates.  I know in the West, it'd be all weird, but in Korea, it's just not.