The "born within the same 12 months" part was, historically, far less a part of America's school system. My grandmother taught grades 1-8 in a one-room small-town schoolhouse. My mother taught both in that little town schoolhouse...and also in a large, modern high school in an industrialized city. There was one h*ll of a difference between the two.

Mom did not mince words about which one she thought was far better for the students - in spite of having a vastly lower per-student budget.