6, so Calstone Light O, and potentially Haru Urara, can copy off of my answers if they want to (though I think it'd be fair to argue they're both unlikely to do that). Issue with this though, is Rulership might be the type to attract the teacher's attention, which means they're more likely to be looking in our direction.

If I had to be a horsegirl for this, I'm gonna pick being Zenno Rob Roy or Manhattan Cafe. If the latter, I'd be fine having Tachyon at 7, to help keep her shenanigans somewhat out of view of the teacher. King Halo might be a good one to sit in 7 as well.

Alternatively, if I was Dream Journey, I'd sit in 3, to run interference between Orf and Donna, keep LaLa from having an outburst at any craziness, and help Marche out.

I think Digitan would pick 5 to keep everyone in view, or 2 if she wants to focus on the class and not be distracted by her oshis (though having Almond Eye of all umas to her left might not be conducive to that). I can also see an argument for her sitting in 4 so she and Kiseki can pass each other notes about what they want to do with their creative endeavors.

I guess the other question would be, if you were the teacher, who would you assign to sit in each seat?