I posted on the other forum too, but here is my thought. Sometimes a DZ may put students and tandems out first because they are making 2 passes. The first pass is typically lower than the second. Students & tandems can take a little extra time in the door and in the interest of safety, they may make 2 passes at 2 different altitudes so students & tandems are taken out of the picture when experienced jumpers exit the plane.
students should exit where they are guaranteed a good spot. i.e not first and short ,and not last and long. if the following group simply looks out the door they can ensure adequate seperation. tandems should always be last ,as the tm has plenty of time to check the spot in freefall,and can dump high if necessary. just my opinion.
That is typically what is done on our DZ too. What we figured out last night was that they were doing that funky exit order (students first) out of a cessna, not out of an Otter so the number of people in the sky isnt as great and there is going to be much more vertical and horizontal separation because of the plane.
I've seen both at the same dropzone. Sometimes the thought is put the tandems/students out first because they pull high and can fly back from farther. Think 2 jump runs in a row - no turn/etc just 10 seconds or so in between.