。
It turned out that she was a clever student.
Literal
She [topic-は] clever student is [quotative-と] became-known.
~と分かる ('come to understand that X / turn out that X') uses the quotative と to mark the content that became apparent. Past 分かった ('became known, turned out') captures the moment of realization or assessment. 聡明 is a slightly literary or formal na-adjective for 'wise / sagacious / clever' — more elevated than 賢い (also 'clever, wise'). The combination signals a positive assessment delivered in a formal register.