When the av beit din (who was second in importance) entered, a row would stand up on either side of him, and would remain standing until he reached his seat.
When the Ḥakham (the third in importance) entered, the students would stand up when he passed by and immediately return to their seats.
Rabbi Yoḥanan explains that this was established during Rabban Shimon ben Gamliel’s term in office, when he was the Nasi, Rabbi Meir was the Ḥakham and Rabbi Natan was the av beit din. Originally the students stood up before all, but Rabban Shimon ben Gamliel was disturbed that the position of Nasi was not given special recognition, so he instituted the above practice on a day that neither Rabbi Meir nor Rabbi Natan was there. When they learned of the change in procedure, they conspired to rectify matters.
The Gemara relates that Rabbi Meir suggested to Rabbi Natan that they ask Rabban Shimon ben Gamliel to teach Massekhet Okatzim – a small set of Mishnayot at the end of Seder Taharot that does not have Talmudic discussions on it in either the Jerusalem or Babylonian Talmud. “Since he is unfamiliar with it” – after the destruction of the Temple, the study of ritual purity lagged and even a scholar like Rabban Shimon ben Gamliel was not expert in it – “we will step forward and proclaim that he is unworthy to be Nasi, and we will move up in our positions.”
One of the students, Rabbi Ya’akov ben Korshei, heard this discussion and was concerned lest it lead to the public humiliation of the Nasi, so he sat down behind Rabbi Shimon and reviewed the material aloud. Hearing laws of purity with which he was unfamiliar, Rabbi Shimon committed them to memory and successfully taught them when challenged to do so by Rabbi Meir and Rabbi Natan. Recognizing the attempt at mutiny, Rabbi Shimon then commanded that they be removed from the beit midrash.
Ultimately it became clear that the students turned to Rabbi Meir and Rabbi Natan for advice and direction even while they were exiled from the beit midrash, so Rabban Shimon ben Gamliel consented to allow them to return, but as punishment they lost the right to have their teachings ascribed to them. Rabbi Meir’s teachings were to be recorded as the words of aḥerim “others,” while Rabbi Natan’s teachings were recorded as yesh omrim “some say.”
The Beit Shmuel explains Rabbi Meir’s epithet as indicating that he started the plan and others followed his suggestion. In his Meromei Sadeh the Netziv points out that it carries with it an oblique reference to the fact that Rabbi Meir was a student of the disgraced, Elisha ben Avuya, who was called Aḥer.
Ben Yehoyada argues that Rabbi Meir and Rabbi Natan were not planning to undermine Rabban Shimon ben Gamliel’s position on a permanent basis, rather they wanted him to recognize the embarrassment of changing the norms and protocols of honor in the beit midrash.