Here are a few other options, depending on the context:
* Discípulo/a: This is a more formal term and often implies a student in a religious setting.
* Aprendiz: This word is often used for someone learning a trade or skill.
* Pupilo/a: This word is usually used for a young student or someone under the tutelage of a mentor.
The best synonym to use will depend on the specific context of your sentence.