We do offer the guideline that your character will need to work hard to improve faster than the class teaches, or even harder to learn magic they aren’t studying in class at all.
Classes are designed intentionally to transmit knowledge to students efficiently and effectively, as opposed to outside sources, which may be written for the already-educated, the layman, the theorist, or the bored. It is also possible to learn, for example, the theory of Sundering without ever learning the practice of Sundering, or vice versa, which is a trap the potential extracurricular learner might fall into. Nonetheless, it is almost impossible not to pick up magics you are not taking classes for, due to constant exposure if nothing else.
no subject
Classes are designed intentionally to transmit knowledge to students efficiently and effectively, as opposed to outside sources, which may be written for the already-educated, the layman, the theorist, or the bored. It is also possible to learn, for example, the theory of Sundering without ever learning the practice of Sundering, or vice versa, which is a trap the potential extracurricular learner might fall into. Nonetheless, it is almost impossible not to pick up magics you are not taking classes for, due to constant exposure if nothing else.