Adverbs refer to the words which modify the verb, adjectives or adverbs, expressing a relation of a cause, time, place and so forth.
Whereas, an adverb clause refers to the group of words which works as an adverb. An adverb clause begins with the subordinating conjunction such as if, although, because and so forth. Lastly, it includes subject and predicate.
An adverbial clause in the above sentence is "who received a good grade".
Subordinate conjunction in the above sentence is 'who' and modifies 'any student'.
