From Heinlein's point of view it seems so - can't be sure anyway.
Guess I carried the idea much to far
If you are interested in that have a look at
http://www.kentaurus.com/troopers.htm.
Nevertheless one of the questions always kept societies going is who should be responsible of acting for the entire society. In fact that leads to the question who should be allowed to vote. So maybe a last note to that:
I guess people allowed to vote should have a certain feeling of responsibility. And according to at least the German law (I know in some countries it might be 21 or maybe sth else) that's the age of 18 so IMHO that's OK.