So that既可以引导目的状语从句,又可以引导结果状语从句,区别是：1）so that引导的目的状语从句中常会有情态动词can,could,may,might,will,would等,而so that引导的结果状语从句中一般没有情态动词；2）So that引导的目的状语从句之前不用逗号,而so that引导的结果状语从句与主句之间往往有逗号相隔开（即略作停顿）.请比较：
He worked hard at his lessons so that he could gain high grades in the exams.他努力学习功课,争取考试能获得好成绩.