First Adulthood

At age 15, humans in the domes are legally adults, and are expected to start moving toward their adult roles. While in many respects they are still considered children, or at the very least immature, First Adulthood is an important stage in any Tholarean's life.
This is the age at which data input for their files become more firm, with less options for change. This is the age when the calculations begin for who the person can be matched with for a marriage, when the determinations start for what job they'll want to train for, and the earliest they can be considered for one of the Insignia. None of these things are set in stone, but this is the first point where someone is meant to become aware of what their options are.
This particular birthday is celebrated with great fanfare, since it's typically a lot more fun than Full Adulthood. It generally takes place in the person's home, with copious numbers of guests coming. Gifts are not expected, but if someone is particularly close they might bring something personalized or homemade.
In the more elaborate parties, the parents and teachers of the new adult will give speeches lauding their accomplishments thus far.
Most parents take the time to privately go over the new information available with their child. The initial data can be exciting to see, but also disappointing if it results in something unwanted. The quiet time of figuring out some of the potential for the future can be overwhelming, but is considered an important part of the process.
Once a child goes through First Adulthood, hitting their fifteenth birthday, they are immediately shifted over to the work training tracks. If they've taken the time to look through the aptitude information, they are granted the option of choosing their own training course.