How does the typical school year in effect today conform to the 19th century notion that students need intervals of rest?

In context, schools today adhere tp the belief that students need rest to cultivate their own ideas, as well as to strengthen their cognitive and analytical skills. Gladwell presents data that he believes is proof this isn't true.

This is the logic the reformers applied to the culti vation of young minds. We formulate new ideas by analogy, working from what we know toward what we don't know, and what the reformers knew were the rhythms of the agricultural seasons. A mind must be cultivated. But not too much, lest it be exhausted. And what was the remedy for the dangers of exhaustion. The long summer vacation, a peculiar and distinctive American legacy has had profound consequences for the
learning patterns of the students of the present day.

Summer vacation is a topic seldom mentioned in American educational debates. It is considered a permanent and inviolate feature of school life, like high school football or the senior prom.