Absenteeism in K-12 schools has remained high following the COVID-19 pandemic and districts need low-cost strategies to improve attendance. In 2020-21, the National Center for Rural Education Research Networks (NCRERN) piloted a personalized messaging intervention in 8 rural districts in New York and Ohio that led to a roughly 2 percent decrease in absenteeism among 1st through 12th grade students, although that decrease was statistically insignificant. We worked with a student information system provider to replicate the intervention in a randomized trial involving K-12 students in 47 districts in 16 states over the 2022-23 and 2023-24 school years. We find that the personalized messages reduced student absences by between 1.7 (p<0.05) and 4.5 percent (p<0.05) and cost, on average, $4.07 per student to implement. We report on implementation challenges and heterogeneous effects across student populations. Our findings have practical implications for implementing technology-based interventions in the rural context.