。
The parents want to give their son the best education.
Literal
Parents [topic-は] son [to-に] best [possessive-の] education [object-を] receive-make-want [quotative-と] are-thinking.
受けさせたい chains three elements: 受ける (receive) + させる (causative: make/let) + たい (want to) = 'want to make him receive.' と思っている frames this as an ongoing intention. The causative させる is key — the parents aren't receiving the education themselves but arranging for the son to receive it.