The Underland Chronicles Worldbuilding: Regalian Education and Life Stages
This all started as a discord chat with @overandunderland and then many many conversations with my wife on how the Regalians grew up and what stages were important/transformative for them. With war, famine & sickness so common, it's probably a pretty big deal for people to get to 20+ years. So I would imagine a lot more emphasis is put on preparing them younger for the world. Luxa mentions that the toddlers are trained how to fly on bats.
I think their society would be more apprenticeship based rather than formal standardized training for everyone. The only thing I think that would be required if able is the military training from 11-14. There's so many times they have to be prepared for an emergency, that it would just make sense that this is a common practice for them to have at least a couple years of basic training.
*disclaimer: Some of this is based on canon, but a lot is made up for fanficiton*