Accessories are fine as long as they are not too large or distracting. As a general rule you should not have anything in your hair that is larger than your bun.
Boys should just try to have their hair neatly off of their face. If your hair is exceptionally long it might need to be pulled up in a pony tail.
If your hair is too short you can secure it in a pony tail and pin it so that it i not sticking out. For performance you might consider making a bun using some synthetic hair.
As long as your hair is secured and up off of your neck and face other styles are perfectly fine. Just make sure they are not a distraction in class.
Watch Mme. Brooksher’s video on the subject.
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