“Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but stupid lasts forever.”
Aristophanes (444-385 BC), son of Philippus, of the deme Kydathenaion, was a comic playwright of ancient Athens.
Other versions include:
“Stupid is forever, ignorance can be fixed.”
“Ignorance can be educated and crazy can be medicated but there’s no cure for stupid.”