In order to encourage my students to turn their homework in on time, I use a system of teams and points. If every member of the team has their homework, the team is rewarded twenty points. If one person does not have the homework, the team loses twenty points. At the end of the week, the students on the team with the most points get to be the classroom helpers for the next week. I don't have to harp on the students that forget their homework because the children work together. The others will usually call the child that normally forgets the homework to be sure their team wins.