they are ---students taht they all performed well in the nat

so 修饰的是形容词, such修饰的是名词.在此题中,diligent修饰名词students, 而such修饰名词短语diligent students. 若题目改为The students are____that they all performed well in the nationwide examinations.则可以填 so diligent.
希望可以帮到你!