Technically,  the issue is concerning employees under 16;  however my view is 16 year olds with a little experience should be able to fill a lot of necessary roles in production agriculture.  That's when I started working out, primarily because my Dad didn't have time to drive me to work before that.

      As to what age or experience level should get any particular job;  I can only speak from personal experience;  but if I applied for a job I know how to do, it generally lasted until something changed. 

     Then I found the next job I know how to do.

     Repeat as necessary...