School staff will receive training on the Unstuck and On Target: High School (UOT:HS) curriculum, and deliver lessons to students during the school day. Interventionists will have the option to participate in ongoing check-ins with study staff. Parents are provided home extensions for each lesson and have the option to participate in trainings delivered by study staff to support generalization of skills to the home environment.

Participants in schools assigned to the TAU condition will continue to receive the standard school-based Individualized Education Plan (IEP) accommodations and school supports that would typically be provided.

Unstuck & On Target: High School (UOT:HS) is a group-based curriculum for high school students that targets executive function skills using Cognitive Behavior Therapy (CBT) techniques. UOT:HS focuses on key functions needed for adult success, such as: self-advocacy, flexibility, time management, motivation, goal setting, developing plans, monitoring progress. Guided practice begins with concrete interventionist support and moves to interventionist cueing, self-cueing, and finally automatic use of the skills without support. Lessons are delivered by school personnel within the school setting. Home extension activities are provided to parents.

Change in Classroom Behavior will serve as the primary outcome at end of intervention. Classroom behavior will be assessed through 15-minute classroom observations conducted by a trained research staff member masked to treatment condition. Observations will occur during the school day in an academic (non-intervention) class. Raters use a standardized form to detect the presence or absence of seven observable behaviors: social appropriateness, on task behavior, initiation, transitions, organization, getting stuck/preservation, expression of overwhelm/negativity.

Change in adaptive behavior will serve as the primary outcome at follow-up (e.g., approximately six month after end of intervention). Adaptive behavior will be measured via parent-report on the Adaptive Behavior Assessment System, Third Edition (ABAS-3). The ABAS-3 is a well-validated parent report measure that assesses practical, everyday skills needed to effectively and independently take care of oneself and interact with others across the lifespan. Performance is represented as standard scores, with higher scores indicating better adaptive skills.

Change in adaptive behavior will serve as the secondary outcome at the end of intervention. Adaptive behavior will be measured via parent-report on the Adaptive Behavior Assessment System, Third Edition (ABAS-3). The ABAS-3 is a well-validated parent report measure that assesses practical, everyday skills needed to effectively and independently take care of oneself and interact with others across the lifespan. Performance is represented as standard scores (mean=100; SD=15), with higher scores indicating better adaptive skills.

The "Executive Function Challenge Task" (EFCT) is an objective and ecologically valid task developed by our research team to assess flexibility and planning skills in a social context conducted by a trained research staff member masked to treatment condition. The EFCT uses a standardized, semi-structured protocol which does not provide explicit rules for completing the tasks to mimic the implicit, unspoken, unstructured expectations in everyday life. The EFCT consists of challenges across several activities and responses are scored on a 3-point scale for each task. The scale (0-good, 1-intermediate, 2-poor performance) has task-specific behavioral markers to guide scoring.