from USA DANCE Rulebook
4.6.3 AGE CLASSIFICATION
188.8.131.52 The following definitions are based on internationally accepted age classifications for Athletes adopted by the IDSF.
184.108.40.206 The following age classifications are based upon the individual's birthday, which occurs within the calendar year:
a) Pre-Teen I: 9th or less
b) Pre-Teen II: 10th or 11th
c) Junior I: 12th or 13th
d) Junior II: 14th or 15th
e) Youth: 16th, 17th or 18th
f) Adult: 19th or greater
4.6.4 PRE-TEEN, JUNIOR, YOUTH, and ADULT classifications:
220.127.116.11 One partner of the couple may be no more than two age classifications younger except in Mixed Proficiency events where only the Athlete must meet the age requirements.
18.104.22.168 Organizers may optionally combine age groups, for example Pre-Teen I and Pre-Teen II. Pre-Teen, Junior and Youth Athletes may compete in the next higher age category actually held at a given competition provided that both Athletes are in the same or separated by only one age classification.
22.214.171.124 Pre-Teen I and Pre-Teen II competitive events must be limited to syllabus events only. This age category is prohibited from dancing Novice, Pre-Championship and Championship events. Closed Gold Championship and Master of Syllabus events may be offered.