Why not?  Oh, its because there are varying levels of "clean" when you deal with students.  When I say kids clean the school, I don't mean they are outside on two story ladders washing windows, I mean they are in the lunchroom after lunch picking up other people's discarded half eaten pbj.  I mean they are in the hallways at the end of school picking up trash that isn't theirs.  I mean they are outside, on school grounds, picking up old cans that have been carelessly disregarded by passers by.  I mean they are given the valuable opportunity to feel what its like to serve someone else who may not even know them, or even care.  I mean they can do something simple that gives them purpose, it gives them immediate positive feedback, and in turn, gives them another check in the "I am valuable" box.  While we are thinking crazy, what about opening doors?  You think we could make a fun competition out of that both in and out of school?  No wait, we could make a game of "please and thank you" where students have to inform teachers (good tattling) at the end of the day, of a time when they heard another student say please and thank you. 

Yes, parents are in charge of teaching their kids how to be nice and courteous and respectful and service oriented.  How much more could we reinforce their model by expanding those learning activities in school?  Just some half eaten pbj food for thought.....that I just picked up after my 2 year olds lunch.  She doesn't know or care that I picked it up, but I love her anyway.