There are typically no specific rules about what type of dress sophomores can wear to prom. It is generally expected that prom attire will be formal, and many students choose to wear dresses or gowns to prom. There is no rule about the length of the prom dress, and sophomores are free to wear long dresses if they choose. Some students may prefer shorter dresses, while others may prefer longer, more formal gowns. Also, some schools organize prom with a particular theme and students must wear dresses according to the dress code. In the end, the choice of what to wear to prom is a personal one and depends on the individual's style and preferences.