what is the latin inscription above the door of the classroom building? and how is it significant?

The Latin inscription over the door states that boys are made into men at Devon School. The irony of this statement is that Gene and Finny do become men, but their maturation comes at great expense. For, Gene lives long with guilt over his shaking the limb that causes Finny to fall and severely fracture his leg. Likewise, Finny matures, but at the loss of his athleticism and with disillusionment in his friend, Gene. After he returns to school and again breaks his leg and lies in the Infirmary; seeing Gene enter, Finny cries, "Are you here to break something else?"

This second break of the same leg on Phineas eventually leads to his death, and Gene carries this guilt for a long time. However, Gene has become a man from this experience.