School Anxiety Inventory for Primary Education: Measurement Invariance and Latent Mean Differences in Spanish Children

School anxiety is one of the most prevalent school attendance problems in Spanish children. Despite its importance, no instruments are available for a precise diagnosis and to establish gender and age differences. This study analyzed the measurement invariance and the latent mean differences of the School Anxiety Inventory for Primary Education (SAI-PE) scores across gender and age in a sample of Spanish children. The sample comprised 1,203 children between 8 and 11 years (M = 10.2, SD = 1.32), selected through random sampling. Findings showed that the SAI-PE presents measurement invariance across gender and age in Spanish children. The latent means analysis revealed that girls scored significantly higher than boys on all SAI-PE dimensions. School anxiety was significantly higher among eight-year-old students. The SAI-PE is the only instrument reliably assessing school situations and anxiety responses in the Spanish child population.