school has 10 distinct synonyms spread across 5 of its 10 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.
an educational institution
“the school was founded in 1900”
a building where young people receive education
“the school was built in 1932”
a body of creative artists or writers or thinkers linked by a similar style or by similar teachers
“the Venetian school of painting”
the period of instruction in a school; the time period when school is in session
“stay after school”
an educational institution's faculty and students
“the school keeps parents informed”
a large group of fish
“a school of small glittering fish swam by”
educate in or as if in a school
“The children are schooled at great cost to their parents in private institutions”
Synonyms, antonyms and the broader and narrower relations for school come from Princeton University’s WordNet. Full sources and licences.
swim in or form a large group of fish
“A cluster of schooling fish was attracted to the bait”