。
The parents raised the child well.
Literal
Parents [topic-は] that child [object-を] skillfully raised.
上手に is the adverbial form of 上手 (skillful) — に converts the な-adjective into an adverb modifying the verb. 育てる (to raise/rear) is the transitive form; its intransitive partner 育つ (to grow up) would make the child the subject instead.