Students with autism spectrum disorder (ASD) studying in mainstream classrooms have diverse adjustment difficulties in learning, social interaction, and emotion regulation. It is crucial to identify the areas these students find most challenging so that teachers can provide training and support accordingly. We therefore developed, examined, and provided norms for the Learning, Social and Emotion Adaptation Questionnaire-Short Form (LSEAQ-S), a teacher report instrument measuring 53 essential adaptive behaviors for mainstream primary school students in Hong Kong. Teachers completed the LSEAQ-S for three samples of 2,298, 2,690, and 3,305 students with ASD from 204 schools and a sample of 1,869 students without ASD from 112 schools. Our study showed that an 11-factor structure best describes the LSEAQ-S, which has high internal consistency and good convergent validity examined with the Social Responsiveness Scale-Second Edition (SRS-2). Normative data of the LSEAQ-S stratified by gender and grade (grades 1 to 3; grades 4 to 6) are presented. Gender and grade differences were found, with girls with ASD lagging behind their same-gender peers in related skills more than boys with ASD did, across both grade levels and especially in senior grades. The LSEAQ-S, together with its normative data, can reveal students' difficulties and needs, inform intervention priorities, and help monitor training progress. LAY SUMMARY: This study introduces the Learning, Social and Emotion Adaptation Questionnaire-Short Form (LSEAQ-S), a teacher report instrument developed in Hong Kong measuring school adaptation of students with autism spectrum disorder (ASD) in mainstream primary schools. The measure helps education personnel identify behaviors in which a student falls behind his/her peers and facilitate training and support targeting those behaviors. Autism Res 2021, 14: 959-972. © 2020 The Authors. Autism Research published by International Society for Autism Research and Wiley Periodicals LLC.