For a general quiet end I would read to the class. Let them pick the book and if they don't like it half way through, ditch it. This works best if they love the book and will actually sigh with frustration when the bell goes! If they like the book and no that they are expected to be quiet then you can have letters being handed out and things being tidied at the same time. I tended to read any letters or do any announcements before reading so that they could go, calm and quiet, as soon as the bell went. But, based on the other things you said it also sounds like they need training first. I would take a couple of weeks and just be prepared to give a bit of time to it at the end of the day. Explain that when letters are being handed out they are expected to be in their seats (reading a book perhaps or listening to you read or doing nothing if they really find it hard) and quiet. If they have a job they must do it quietly and quickly or someone else will be asked to do it. As soon as they chatter or get out of their seats the whole class freezes, waits for quiet and then continue. No letters will be handed out and no body will be going home whilst people are not doing as they are asked.If kids doing jobs or handing out are distracting take the letters and make them sit down. If you plan to give yourself 20 mins or so at the end of the day then you wont be stressing about getting them out on time and will be able to do the 'I can wait' voice in a more genuine way! Keep at it, every day for a couple of weeks. If this doesn't suit then I would suggest giving out jobs and getting the others involved in a game, perhaps on the carpet if you have the space.