Yoma, Chapter One, Mishnah Three
This mishnah describes how the elders educated the high priest during the week that preceded Yom Kippur. We can easily note that the rabbis anticipate that the high priest will be completely uneducated in Torah and in the proper ways of the Temple service. Indeed, they dont think that he even knows how to identify common sacrificial animals! According to the traditional understanding of this mishnah, the high priests that served in the Second Temple period were appointed by the kings out of political considerations and not for their expertise in Temple practice or for their personal piety. This is largely corroborated out by other descriptions of the high priests in such writings as Josephus and other historical works. However, the rabbis description of the high priests utter ignorance may be exacerbated by the Second Temple rivalry between the Pharisees, the rabbis spiritual forefathers and the Sadducees, a sect to which many high priests belonged.
Another interesting way of understanding this mishnah is to note the tension between the genealogically transmitted priesthood and the Torah which is transmitted from teacher to pupil and not necessarily from father to son. The rabbis generally favored the relationship of teacher to pupil even over that of father to son but also realized that the priesthood was genealogical. In the high priest who must serve in the Temples most critical service even though he was an ignoramus these two values distinctly clash.
Section one: They delivered to him elders from the elders of the court and they read before him [throughout the seven days] from the order of the day. And they say to him, Sir, high priest, you read it yourself with your own mouth, lest you have forgotten or lest you have never learned.
Section two: On the eve of Yom HaKippurim in the morning they place him at the eastern gate and pass before him oxen, rams and sheep, so that he may recognize and become familiar with the service.
Section one: During the week that precedes Yom Kippur the elders read to the high priest from Leviticus 16 so that he will understand how to perform the service. Even if he professes to know what to do, they tell him to read it himself, or perhaps to repeat what they say to him, lest he might have forgotten it or lest he never read the portion in the first place.
Section two: On the eve of Yom Kippur they show him various animals so that he will know which ones are which and which ones are offered for which sacrifice.