The term "high-grader" can be replaced with various synonyms depending on the context. For example, a person who is stealing the highest-value minerals from a mine can be referred to as a "ore thief" or "mineral smuggler." Meanwhile, a student who consistently achieves high grades may be called a "top-performer" or "high-achiever." In legal terms, high-grading can be referred to as "theft of valuable resources" or "illicit mining practices." Other possible synonyms include "gold thief," "high-value material extractor," "elite student," "top student," "scholar," and "honor student." It's important to choose an appropriate synonym based on the context to convey the intended meaning accurately.