One rule I enforce is one student per chair.
Yes, sometimes students try to share chairs. They'll go halvsies or one student will sit in another's lap. Both are okay with the arrangement and not pleased when I break them up. (There are enough chairs in the room so that each student gets his/her own.)
It was a government class. All seniors. They had the assignment, and I took a seat at the front of the room.
I noticed the boy looking at me. He hadn't raised his hand; he was just regarding me like he wanted my attention. Once he had it, he pointed to the girl on his lap. (Something I should have noticed before this. I'll blame it on where I sat versus where he sat--angles of sight and such.)
Once the girl found her own seat, the boy thanked me. "I'm just too nice."
I couldn't figure out why he didn't get rid of her himself if he didn't want her there. They were both seniors. He was a large guy.
But the girl was pushy. I noticed this as the period wore on. She shoved and pushed her way to where she wanted to go and what she wanted to do.
Sometimes my job is to be the one to say no.
I kept my eye on the girl for the rest of the period. Waited. She didn't try anything more with the boy who clearly did not want her attention.