From the USABDA rulebook:
4.5.2.1. A CLASSIFICATION PROFICIENCY POINT is awarded to Amateur Athletes at Recognized Competitions who either:
a) Place first in their current classification if a semi-final was danced.
b) Place first, second or third in any higher proficiency level of the same age group and style if a semi-final was danced.
c) Danced in the finals of any higher proficiency level of the same age group and style if a quarter-final was danced.
Under the USABDA system, you place out of a level once you have accumulated 3 points in it. Somewhere else it mentions that you also place out of a level by winning it at USABDA Nationals - ie, Nationals is worth 3 points. "Recognized Competition" currently means anything with a USABDA or NDCA sanction - unsanctioned college comps don't count.
Given the frequent lack of semifinals, people accumulate USABDA points _very_ slowly.
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YCN/NECN or collegiate points are a fairly different system. Here you can dance in a level until you earn 7 points, but they are easier to get.
from memory:
a) if a semifinal was danced, 1st place gets you 3 points, 2nd place 2 points, and 3rd place one point
b) if a quarterfinal was danced, 4-6th places also earn you 1 point.
c) Points earned in one level are worth twice as much in the next level down, and 7 points in every level below that. So earning one point in gold counts as 2 in silver, and 7 in bronze.
d) Regardless of all these details, if you have placed out of a level under the USABDA/NDCA system you are not allowed to dance that level under the collegiate system either.
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Here's where it gets complicated:
Collegiate points are generally calculated based on the results of all the organized but unsanctioned college comps someone has entered. Many people have also done USABDA or NDCA adult comps, and there is a disagreement about how to handle that. The people USABDA appointed to advise YCN say that 1 USABDA point should translate as 1 YCN point. But a lot of the collegiate teams (who as comp organizers hold the only real power) think that makes no sense as it's a lot harder to earn points at an adult comp than at a collegiate one. Instead, for the purposes of elgibiliity at something like the MIT comp, you have to calculate collegiate points for your USABDA and NDCA placings as if they had been collegiate comps (so, first gets you 3 points, not 1).
Hang on, we're not done yet:
There are also a few collegiate competitions, such as Harvard and sometimes BU, which base elgibility decisions on USABDA/NDCA points, rather than collegiate points. But because these competitions are not sanctioned by either of those bodies, they cannot award points under that system. So you could theoretically win a category every year at Harvard and never place out of it. Despite the fact that these comps don't look at collegiate points, the other collegiate comps consider placing at them to award collegiate points.