The antonyms for the phrase "are the same class as" can vary depending on the context. In terms of education, antonyms could be "are in a different grade," "are in a different level," or "are in a different program." In terms of social class or status, antonyms could be "belong to a different social class," "are from a different background," or "are of a different status." Alternatively, if the context is more general or open-ended, antonyms could include "are completely different," "are unrelated," or "are from distinct categories." The antonyms for "are the same class as" can vary widely depending on the subject matter and the intended meaning.