* Estudio: This is the most straightforward translation, meaning "study." It's suitable if you're referring to the act of studying, or a period *dedicated* to studying. However, it doesn't specify a supervised setting.
* Sala de estudio: This translates to "study hall" more literally, meaning "study room." This is a good option if it's a designated room for studying.
* Tiempo de estudio: This means "study time," and is appropriate if you're talking about the scheduled time for studying.
* Clase de estudio: This translates to "study class," which might be accurate if the study hall is a supervised class with an instructor.
Therefore, the best translation depends on what you want to emphasize. If you can provide more context (e.g., "Is it a supervised study period in school?"), I can give you a more precise translation.