supposed to do sth（be supposed to do sth）

1、1.be supposed to do= should do 应该做某事：you are supposed to go to school on time=you should go to school on time.你应该按时上学。

2、2.be supposed to have done sth= should have done. 应该做成了某事（实际上没做成）：You are supposed to have done your homework= you should have done your homework.你本应该能完成作业的。