This is a hard one and is personal to the school. My school does a shed lad of stuff. Most pupils are fine: supportive families, good work ethos etc. And then there are parents who are a challenged as their children! We have rewards (trip to a theme park for the best forms as well as individual rewards for over 95% attendance) and sanctions (detentions, meetings with parents). Our most effective system is the parent-liaison mentors who actually find out what's going on in the family and say that it actually doesn't matter...the young person HAS to attend school while also trying to help. These people love their jobs and have my respect (I am the SENCO).