I belong to a Baptist church, and Baptists don't have confirmation ceremonies.
To join a Baptist church, first a person publicly tells the membership that he or she has accepted Jesus as Savior.
Then, the person is baptized by total immersion.
Then, the person can join the church. The person has to request to join the church in front of the membership. Then, the Pastor asks the person are you saved, and have you been baptized by total immersion (in that order). Then, if the person is an adult, the Pastor also asks if that person has read, understood, and agreed with the church constitution and doctrinal statement. If the person says "yes" to all the questions, then the Pastor asks the membership to vote by raising their hands. That's how a person becomes a member of the church.
New Christians are discipled by other church members, especially in their Sunday School classes.
Children and adults learn about the doctrines in Sunday School and church. There is no special age for this. Teaching is for everyone. So we don't have confirmation classes.