Teachers in the intervention group will receive the Incredible Years-Helping Preschool Children with Autism program (IY-HPCA).

They will participate in a 6-session group-based face-to-face intervention. Sessions will last 3 hours, will be delivered weekly at Hospital Sant Joan de Déu, and will be led by two trained co-leaders. The following main topics will be covered: (1) language development, (2) social interactions, and (3) emotion literacy and self-regulation.

Two groups will be conducted, and each of them will include around 10 teachers.

The control group will not receive the intervention. Teachers who are assigned to the control group will continue their usual teaching practice.

No restrictions will be placed on schools regarding access to other training and support services during the course of the study, but this information will be monitored as a potential confounder.

Teachers who are assigned to the intervention group will be asked not to share the intervention contents with other teachers who are in the control group before the end of the study.

The IY-HPCA® program is a face-to-face 6-session group-based intervention for preschool teachers of children aged 2-5 with ASD or language and communication difficulties. Sessions last 3 hours, are delivered weekly, and are led by two trained co-leaders who have experience working with children on the autism spectrum. The program covers three main topics: (1) language development, (2) social interactions, and (3) emotion literacy and self-regulation. Teachers learn about coaching language, imitation, sensory routines, social communication, use of pretend and puppet play, and self-regulation skills. Visual supports such as picture schedules, choice cards, command and feelings cards are used, and practices are tailored to children's communication and play level stages. The intervention is structured and includes role-playing techniques and video visualization.

Teachers' attendance at the sessions will be regeristered weekly with a sheet of attendance, with the aim to determine levels of compliance and engagement with the intervention. An attendance of at least 4/6 sessions is expected, with a minimum of 50% of teachers finishing the program.

Teachers' compliance and satisfaction with the intervention will be assessed weekly after each session with the questionnaire "Incredible Years Teacher Weekly Evaluations", which is part of the IY-HPCA® program materials.

This weekly assessment asks teachers to rate their satisfaction with different aspects of the program.

Teachers' acceptability and satisfaction with the program will be assessed with the Final Participant Satisfaction Questionnaire-Helping Preschool Children with Autism Program (included within the IY-HPCA® program). Data will be collected after the last session of the intervention.

Individual interviews will be conducted after the last session of the intervention to explore from a qualitative perspective: (1) teachers' acceptability, satisfaction and overall experience and perceptions of the intervention, and (2) teachers' perceived changes in their skills after the intervention.

Outcome measurements 3 and 4 will be combined to determine teachers' experiences, acceptability and satisfaction with the program.

The Teacher Strategies Questionnaire for Children with Autism (TSQ-A) is a 52-item teacher-report questionnaire part of the IY program materials that consists of six sections. The first section asks teachers to rate their confidence in promoting social, emotional, language and academic development of children with ASD. Sections 2-4 ask teachers to rate the frequency with which they use teaching techniques to support children's language, social and emotional development. In the last section, teachers rate the frequency of their planning and support strategies according to a five-point scale.