De pueris inter quos educabitur ille huic spei destinatus, idem quod de nutricibus dictum sit. de paedagogis hoc amplius, ut aut sint eruditi plane, quam primam esse curam velim, aut se non esse eruditos sciant. nihil est peius iis, qui paulum aliquid ultra primas litteras progressi falsam sibi scientiae persuasionem induerunt. nam et cedere praecipiendi partibus indignantur et velut iure quodam potestatis, quo fere hoc hominum genus intumescit, imperiosi atque interim saevientes stultitiam suam perdocent.
(Quintilian, Inst. Or. 1.1.8)
As regards the boys in whose company our budding orator is to be brought up, I would repeat what I have said about nurses. As regards his paedagogi*, I would urge that they should have had a thorough education, or if they have not, that they should be aware of the fact. There are none worse than those, who as soon as they have progressed beyond a knowledge of the alphabet delude themselves into the belief that they are the possessors of real knowledge. For they disdain to stoop to the drudgery of teaching, and conceiving that they have acquired a certain title to authority—a frequent source of vanity in such persons—become imperious or even brutal in instilling a thorough dose of their own folly.
* There is no translation for paedagogus, the slave-tutor. “Tutor,” “guardian,” “governor,” and similar terms are all misleading. He had the general supervision of the boy, escorted him to school and elsewhere, and saw that lie did not get into mischief, but did not, as a rule, direct his studies.
(tr. Harold Edgeworth Butler, with his note)
Crambe Repetita 