The Bar/Bat Mitzvah ceremony is a marking of the coming-of-age of a child, for boys at 13 and for girls at 12, that marks the development of a child into an adult. The children put in months of effort to learn the ins and outs of the proscribed mitzvahs and the importance of learning them so as to deepen the meaning of what it means to be Jewish.
Boys learn how to wrap Tefillin, and upon fulfillment of the ritual of Bar Mitzvah, which usually involves reading a portion of the Torah (maftir) and a portion of one of the book of Prophets (haftorah) the young man is counted as part of a minyan (one of the ten men needed to perform certain rites and rituals of daily observance).
It's a tough age to get kids to sit in their seats to learn from the rabbi, and it requires incredible patience on the part of the rabbi to teach kids whose hormones are just beginning to rage.
