I have been in small spear formations for sparring bouts (viking era skirmishing but a spear is a spear) and they are indeed very efficient even with little to no training. The same goes for one-on-one btw, a spearman with little experience can still beat a seasoned swordsman quite often.

Edit; to clarify, I mean a swordsman with a longsword or a viking-type sword and round shield. I presume the big roman shield that covers almost the entire body would be much more advantageous.