How can a law clerk be distinguished from a legal assistant?

A law clerk is usually a law student, either in or finished with law school, waiting to take or receive passage of the Bar, working (usually writing or doing research) for another, already licensed attorney. In California, the terms "legal assistant" and "paralegal" are interchangeable in the Business and Professions Code. A "paralegal" is an entirely different animal to a "law clerk". Paralegals (usually) have not been to law school and do not qualify to take the Bar Exam.