What's the difference between the 2 sentences?He finished school at fifteen.and he had finished school at fifteen.what's the difference ?

What's the difference between the 2 sentences?He finished school at fifteen.and he had finished school at fifteen.what's the difference ?
What's the difference between the 2 sentences?
He finished school at fifteen.and
he had finished school at fifteen.
what's the difference ?

What's the difference between the 2 sentences?He finished school at fifteen.and he had finished school at fifteen.what's the difference ?
第一句,他在十五岁的时候完成了学业,强调那时候他十五岁
第二句,他在十五岁时就已经完成了学业,强调他十五岁时已经完成,但是不一定就是十五岁的时候完成的,也可能是14岁或者再往前