class has 17 distinct synonyms spread across 7 of its 9 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a collection of things sharing a common attribute
“there are two classes of detergents”
people having the same social, economic, or educational status
“the working class”
education imparted in a series of lessons or meetings
“he took a course in basket weaving”
(biology) a taxonomic group containing one or more orders
elegance in dress or behavior
“she has a lot of class”
arrange or order by classes or categories
“How would you classify these pottery shards--are they prehistoric?”
Synonyms, antonyms and the broader and narrower relations for class come from Princeton University’s WordNet. Full sources and licences.