Agreed in those days we sat at (or rather in, they were the all in one double fold-down bench type) desks arranged in rigid rows and columns, naughty/dim children at the front, clever/placid children at the back, and stayed there – no wandering about like today! But it was still necessary for teachers to do a certain amount of keeping the lid on things.
They did this by very firmly stamping their authority on proceedings. Retribution for stepping out of line had to be instant and fairly brief, so CP was ideal. The children most likely to get it were seated near the front anyway, and it only took a moment to order (or drag) them out to the front of class, whack away, and send them back to their seat, or, for additional emphasis, to stand in front of the class facing the wall.