What is the symbolism of the Ceremony of Eleven in The Giver?

While Jonas feels that the Ceremony of Eleven is "not one of the more interesting ones"(46), it does seem to mark the end of prepubescence and the beginning of adolescence as well as an educational advancement.  

Elevens are given new clothing. The females get "different undergarments" (46), and the males get "longer trousers" (46). This reflects the changes that come in adolescence for females and males. It should also be noted that this seems...

While Jonas feels that the Ceremony of Eleven is "not one of the more interesting ones"(46), it does seem to mark the end of prepubescence and the beginning of adolescence as well as an educational advancement.  

Elevens are given new clothing. The females get "different undergarments" (46), and the males get "longer trousers" (46). This reflects the changes that come in adolescence for females and males. It should also be noted that this seems to be the general period when the children begin to experience Stirrings, their first hint of sexual desire. In the story, Asher is already on medication for his Stirrings, and Jonas, almost twelve, has just experienced his own first Stirrings.  So, the Ceremony of Eleven does symbolize the beginnings of adolescence, even though the community has not been able to impose Sameness on the date on which this happens. 

The Elevens' clothing also comes with a special pocket to hold a calculator, which is presented during the ceremony. I think this symbolizes a kind of intellectual "coming of age" for the children, too. In many schools, children are not permitted to use calculators until they have mastered the basic operations of math, and being given a calculator suggests this mastery has been achieved and it is time to move on to higher math. 

Jonas' attitude toward the Ceremony of Eleven, that it was not particularly important, is largely based on his perspective as he approaches the Ceremony of Twelve, at which he and all the other children will receive their assignments for their life's work.  Nevertheless, the ceremony is important, representing a physiological and educational coming of age.