Some history of bat/bar mitzvahs... "Bar Mitzvah" did not exist in biblical times. A child began to observe commandments when he or she showed an understanding and the ability to fulfill the commandment.  By the late Middle Ages children had stopped participating in religious requirements or customs.  A decision was later made to have children become responsible at the age of Jewish maturity.  16thC. is the earliest reference to calling a boy to the Torah on Shabbat around his 13th birthday.  Jewish customs are primarily directed towards men but things are beginning to change.  The first modern Bat Mitzvah was in 1922, in the United States.  It was the daughter of Rabbi Mordecai Kaplan, the founder of the Reconstructionist movement.  (As in Christianity there different 'branches' of Judaism, e.g. Orthodox, Conservative, Reform, Chabad.)  Jewish law established the age of maturity for girls at 12 and boys 13 but different Synagogues have different customs.