that's the way it is in our Conservative synagogue. we have Hebrew school from Kindergarten through 7th grade -- though most kids wait until 3rd grade to start. the kids have to go twice a week after school and must attend a certain number of junior congrregations sessions on saturday mornings. at various times throughout the year one of the Hebrew school classes will elad Friday night, Saturday morning or Saturday evening services. the kids learn religion, how to read a prayer book in Hebrew, Jewish history and culture, and all about Israel.
the bar or bat mitzvah candidate has to attend all those Hebrew school classes, and then in the year before the bar/bat mitzvah they are tutored in the prayer service they will lead (in Hebrew and English) including the portion of the Bible they will read in Hebrew before the entire congregation. the bar/bat mitzvah student also has to prpeare a speech which serves as a "teaching moment", i.e., they explain the Bible portion and how it relates to their lives. and the speech is also used to thank parents and teachers and etc. for helping the student reach this moment, which significes that he or she is now ready to assume adult responsibilities within the Jewish community.
it's also customary for the bar/bat mitzvah student to perform community service and/or to make a donation to charity.