To prepare youth for the "next level" of church membership (when they're invited to receive Holy Communion), 6th through 8th graders review the doctrines (teachings) of the Bible as summarized in Luther's Small Catechism.
The historical practice of "confirmation" is when a member promises to remain faithful to the teachings of the Bible and to regularly attend worship and Bible study. This normally occurs after 3 years of instruction and sometime around the end of middle school.