As a growing base of evidence links student success with attendance, many states have chosen to include measures of student absenteeism in their accountability systems under ESSA. Consequently, school districts face strong incentives to improve attendance. We report on a randomized field experiment in which parents of early elementary students received personalized information about the academic content their child missed while absent. Following an absence, school staff sent postcards to parents detailing how many days of school their child had missed alongside a handwritten note from their teacher summarizing the academic material covered during the absence. We randomized the intervention across schools and classrooms in two urban school districts. The analysis sample included 5,552 students in preschool through second grade. Overall, the treatment reduced absences by 8.3% (95% CI, 2.6-14.0%). The results provide evidence that a postcard intervention designed and implemented by schools and teachers rather than 3rd parties can be effective in reducing absences. The teachers' annotations with personalized academic and absence information are a unique feature of the intervention that suggests areas for further research.