Teen's & dance school underwear rules under dance leotards

Many dance schools ask their students to not wear panties under their dance class leotards and costumes. But why do they ask this? And what do teenagers and adults then do when they are menstruating?

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shorts Teen's & dance school underwear rules under dance leotards & costumes

Should my kid wear underpants, under their dance leotards and costumes?

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Teen's & dance school underwear rules under dance leotards & costumes #shorts