USA Volleyball Juniors website link

USA VOLLEYBALL JUNIOR OLYMPIC AGE DEFINITION
For use during the 2011-2012 Season
Once a player participates in a club or varsity program for any university, college, community college, or junior college, he/she is ineligible to play in any regional or national JOVC qualifying and championship events.

18 and Under Division:
Players who were born on or after September 1, 1993
or
Players who were born on or after September 1, 1992
and a high school student in the twelfth (12th) grade or below during some part of the current academic year
17 and Under Division:
Players who were born on or after September 1, 1994
16 and Under Division:
Players who were born on or after September 1, 1995
15 and Under Division:
Players who were born on or after September 1, 1996
14 and Under Division:
Players who were born on or after September 1, 1997
13 and Under Division:
Players who were born on or after September 1, 1998
12 and Under Division:
Players who were born on or after September 1, 1999