Shell script problem

Hello,

I would like to create a Shell script that shows the disk space used by each users.

I would like to show it like this:

UserName1 : disk space used
UserName2 : disk space used
Username3 : disk space used

I tried with du and cut but I would like to try something else. Thank you.

Your son is a girl studying in computer science. This is a homework for the linux class. Nobody found the answer yet and it's for next week. 

I can do it by doing du on passwd and by using cut. But I feel like it's not the way that the teacher wants.