Meaning

This is a joke, and a good one. The brain supposedly works constantly and tirelessly, right up until the moment a person walks into a classroom, at which point it apparently shuts down. Frost is gently mocking the gap between natural, engaged thinking and the kind of passive numbness that formal education can sometimes produce. The humor lands because many people, students and teachers alike, have felt exactly that disconnect.

Context

Frost spent a significant part of his life as a teacher and was deeply engaged with questions about education, learning, and the conditions under which the mind genuinely thrives. His criticism here is light but pointed. He seems to be suggesting that conventional schooling can work against the very curiosity it claims to encourage. The line belongs to a tradition of gentle, affectionate educational satire, and it resonates because it contains a recognizable truth dressed up as a throwaway quip.

About the author

Robert Frost taught at several institutions over the course of his career and held a complicated but genuine relationship with formal education. He was widely celebrated in his lifetime, winning the Pulitzer Prize for Poetry four times and becoming something of a national literary figure in the United States. Known as much for his humor and plain-spoken wisdom as for his poetry, Frost had a gift for packaging insight inside a laugh, and this line is a small but perfect example of that ability.