Read the school handbook and see what procedure should be followed when a child is going to be absent. It helps if a parent calls in an absence a half hour before the start of school. If a phone call is not received, the school calls the parent. This insures that if the child was sent to school, nothing happened along the way and that the child is not skipping school. At the beginning of school, an emergency card is filled out with people who may be contacted if an emergency occurs. If the child is absent and the parent cannot be contacted, the backup person is called to determine the child's whereabouts. At first this can be very time consuming, but parents must understand that it is about the students' education and safety.
Another effective technique is to publicize the percentage of students absent on an average day and set a goal to improve. Tell the students what the percentage is. Set an 'attendance' goal and have them draw a big graph that charts progress. The more involved they are in solving the problem, the more likely it is that the problem will diminish.