Legal Question in Intellectual Property in California

You would be infringing someone's copyright in the test materials, probably that of the instructor or the school.

No. It is absolutely not legal. It probably also violates various student codes of conduct, and could subject the student(s) to discipline from the school.

Instructors, in most cases, retain copyright in the tests they create. Moreover, many courses use test material made available by the publisher of the text books. Those publishers own copyrights in the test material.