答案：B

分析句子结构可知：句子________ made the school proud缺少主语，另外还要引导主语从句，故此只能选择what，由此先排除C、D两项答案。再结合句子________ more than 90% of the students had been admitted to key universities结构完整不缺少成分，只需要引导词。所以选用that。