In chapter 6 of The Giver, why is the entire community going to the auditorium?

When the chapter begins, Jonas and his family are putting
on their nicer clothes. Jonas' mother is worried about Lily's ribbons becoming untied,
and it is clear that she wants everything to look good. Eventually the reader finds out
why. Jonas's family is getting ready to head to the Auditorium, where there will be a
series of ceremonies. The text says that this event happens only once per year, and that
all of the working adults get two days off of work for
it.

The ceremonies are focused on the children and their
advancement to the next age and the responsibilities and privileges that it brings. The
first ceremony is the ceremony of the naming. This is the ceremony where the youngest
children are placed into their chosen families. The ceremony that is the biggest deal of
all is the ceremony of the twelve. This is the ceremony that declares what the job of
each new twelve-year-old will be.