so that 的意思是in order to,"为了,以便"
He tries his best so that he can pass the exam.
(主句和从句时态保持一致即可)
以上句为例,改为简单句：He tries his best,becuse he wants to pass the exam.
根据句意改变,不需要改变时态.
这个词组要注意的是和so.that的区别.（如此.以至于）
如：She is so kind that all the students like her.
她是如此善良以至于所有的学生都喜欢她.