Not everyone works well in groups or alone. I feel the children should have a choice in the beginning of the year until the teacher or para observes and makes note of what works best. I would also explain to the children that sitting next to your best friend isn't always a good choice and can be distracting. Students in wheel chairs need extra room to move around so having tight rows of desks or cramped areas wouldn't be beneficial. Those with poor vision or hearing should be towards the front of the classroom so they don't miss and instruction or the lessons.
Younger students do well in my opinion, working in groups and with the teacher. From my experience working in first and third grade classrooms, I observed a lot of group work done. Usually the groups were divided by table or abilities. This was common for reading and math activities. The paraprofessional would be needed to work with the groups who struggle and need the extra guidance to be kept on track. I believe children are smart and knowledgeable, but a lot of distractions keep them from shining. One student I worked with loved to talk and was off task a lot and I was responsible for making sure the student focused and followed directions. Older students do a lot of independent work and when in groups it is typically for projects.
In a perfect world, in a perfect classroom, every