In the US, there should be mandatory military service. Mandatory school should end at 14 and they go into the military. For four years, they specialize based on their skills and intelligence.

You can delay it by going to a private, tuition based High School, bringing finishing schools back. If you do this, you still have to be in the military for 10 years, but you become an officer rather than enlisted.

Refusing to enlist or trying to escape the country will be considered Treason