I do the groups of 4, but don't always like that arrangement.
I REALLY like the hoseshoe or U. Basically have a back row and the sides going up looking like a U ~ sometimes I need to place a student or two on the inside of the U, but it works well!
I also like rows where the desks are pushed together in rows of 3 or 4 such as ~~
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and I follow that pattern in the back until I have all kids in lines.