Native speakers seem to do fine. Learning a language while growing up, having the Hiragana as a helper, while all your media is written in Japanese makes everything easier. When they finish school they know enough Japanese to go by. It's obviously different for non-native people.
Also, it's not like you stop learning even after school. For example English has according to the Oxford dictionary 171,476 words in current use excluding inflections, and several technical and regional vocabularies. Does all English university students know these words?
Also, it's not like you stop learning even after school. For example English has according to the Oxford dictionary 171,476 words in current use excluding inflections, and several technical and regional vocabularies. Does all English university students know these words?