If you are segmenting for events such as Junior Jumpers or graduation, it's important to just target the relevant age groups. Make sure the all segments are set as Dynamic!
Some most-used age groups are shown below. To calculate anything else, multiply Age x 365.
"Kids 6 & Under" segment
- Birthdate in the last 2190 days
- Customer_type is one of Kid *
"Kids 7 & Older" segment
- Birthdate over... 2555 days ago
- Customer_type is one of Kid *
"Kids 16-18 years old" segment
- Birthdate over... 5840 days ago
- Birthdate in the last 6934 days
* For this criteria, if no options are appearing in the dropdown, go to Configuration > Settings, find the Customer_type attribute, click on the three little lines that appear in that row, & click generate. You should see "Kid" and "Parent" appear. Don't forget to hit the Create button to save!