What exactly is the “rite of passage” to which Sharon Olds' poem, "Rites of Passage" refers?

The poem "rites of passage", by Sharon Olds, depicts the birthday party of her first grade son. As the poem goes on, one can see the metaphoric imagery laid in to resemble the coming of age for a man. Men will have "hands in pockets" as "they stand around jostling, jockeying for a place" in the world.

The poem, for me, seems to be one which pokes fun at the assumptive role a man must play when surrounded by other men. This being said, the boys here are learning at a young age that they must fill the role early so as not to lose their self-recognized place in society.

The poem does not speak to the norm in regards to a first grade birthday party. Instead, it speaks to the rite of passage that a boy must take to become a man.