Drafting/Technical school of that day would start you on a classroom drafting board about 18" X 24" and 36" X 24".
Those boards were only suitable for A, B, and C sizes drawing sheet (i.e.
8½" X 11", 11" X 17" and 17" X 22"). A 24 inches T and small squares were adequate enough.(The one I have now is 36 inches long)
However the Ship building and Aircraft industries required layouts and assembly drawings larger than E size drawing (34"X 44"). At that time, corded parallel bar and T square were not adequate for an 8 foot long drafting table. Not to mention that most of the time piles of reference drawings were stacked at one end of the table.