Under the new USA Dance rules, there is no requuirement for a specific proficiency level or competition placement. If you pass what is basically the ISTD teaching exam, you can teach and still compete in USA Dance events, however you will not be able to do NDCA amateur events. Nor would you be able to do NDCA pro events, or USA Dance will reclassify you as a professional.
The exam is a major challenge and a worthwhile one to work towards, no matter if you stay true amateur, pursue teaching under the special provision, or declare yourselves professionals.