是省略了that,但不是同位语从句,而是定语从句句子相当于,the opportunity that the school education affords usopportunity在从句里作宾语,因此that可以省略,也就是the school education affords us the opportunity for making friends.同位语从句可以是这样的,Its greatest advantage is perhaps the opportunity that we can make friends in school. 这里从句描述的就是opportunity,此时that 不可省略。