* School-sponsored events: Many middle schools will have specific days (like Halloween or a themed spirit week) where costumes are allowed, often with guidelines on appropriateness.
* Regular school days: Generally, costumes are *not* allowed on regular school days. Middle schools typically have dress codes that prioritize neat and appropriate attire for learning.
To know for sure, you should check your school's dress code policy (often found in a student handbook or on the school website) or ask your teacher or school administrator.