The antonyms for the phrase "gold stars" could be expressed in several ways, depending on the context. For example, if we consider the phrase to mean praise or recognition for good performance, antonyms could include criticism, disapproval, or failure. On the other hand, if we interpret "gold stars" as physical objects, antonyms could be what they are not, such as plastic stars or no stars at all. In any case, it is essential to understand the context and intended meaning when searching for antonyms, as they may differ depending on the level of abstraction and the language used.