In every fighting class, the top students rise to the top, but there can only be one who is considered the best. That's determined simply by having them fight... and the one who quits or is knocked out, will stay in her place as just another girl in the dojo, and everyone will know who the top girl is. Kicks, holds, it's all here to determine the top student.
A final submission gained, but winning alone doesn't make a top student, it's humiliating your opponent so they know their place. The other girls watch as our winner thoroughly dominates the loser and finishes her off.