Table 1.

Outcome measures.

Participant type	Measure – PRIMARY	Timepoint (baseline, 20, and 52 weeks)
Associated teacher/TA	Social Skills Improvement System (SSIS) (Gresham & Elliott, 2008) scales: Social skills scale (PRIMARY OUTCOME MEASURE). 46 items, higher scores indicate greater social competence. Social skills including social communication, co-operation, social engagement, empathy, assertion, responsibility and self-control are measured.	20 weeks
Participant type	Measure – SECONDARY	Timepoint (baseline, 20, and 52 weeks)
Associated teacher/TA	Social Skills Improvement System (SSIS) (Gresham & Elliott, 2008) scales: 1. Social skills scale. 46 items, higher scores indicate greater social competence. Social skills including social communication, co-operation, social engagement, empathy, assertion, responsibility and self-control are measured. 2. Problem behaviours scale. 30 items, higher scores indicate fewer problem behaviours. Academic competence scale. 7 items, higher scores indicate higher academic competence.	All (social skills scale at 20 weeks is primary outcome)
	Strengths and Difficulties Questionnaire (SDQ) (Goodman, 1997). 25 items, higher scores indicate a higher chance of developing a mental health disorder.	All
	Bespoke resource use questionnaires capturing resource implications of ‘usual support’ received by ACYP in both arms of the study. *Specific questions were included at 20 weeks to assess any adverse events	All *20 weeks only
Facilitator teacher/TA (intervention arm only)	Bespoke demographic information form collecting demographic information and training and experience of the facilitator teacher/TA.	Baseline only
	Bespoke resource use questionnaire capturing resource implications of running the LEGO® based therapy sessions at school. *Specific questions were included in the session resource use questionnaire to assess any adverse events potentially attributable to the intervention.	After each session
	A fidelity checklist based on the existing treatment manual (LeGoff et al., 2014). 17 items, higher scores indicate higher treatment fidelity.	After each session
	A bespoke questionnaire to assess acceptability of the intervention structured around the Theoretical Framework of Acceptability (Sekhon et al., 2017). 11 items, higher scores indicate greater acceptability.	20 weeks only
Autistic child/young person	Multidimensional Scale of Perceived Social Support (Zimet et al., 1988). 12 items, higher scores indicate a higher degree of perceived social support.	All
	Asher Loneliness Scale (Asher et al., 1984). 24 items, higher scores indicate lower levels of loneliness and social dissatisfaction.	All
	Child Health Utility 9D (CHU-9D) (Stevens, 2011). 9 items, higher scores indicate higher health utility.	All
Parent/guardian	The Social Communication Questionnaire (SCQ) (Rutter et al., 2003). 40 items, higher scores indicate more social communication difficulties.	Baseline only
	SSIS (Gresham & Elliott, 2008) scales: 1. Social skills scale. 46 items, higher scores indicate greater social competence. Problem behaviours scale. 33 items, higher scores indicate fewer problem behaviours.	All
	SDQ (Goodman, 1997). 25 items, higher scores indicate a higher chance of developing a mental health disorder.	All
	EQ-5D-Y (3 L proxy version) (The EuroQol Group, 1990). 5 items, higher scores indicate higher health utility.	All
	Bespoke resource use questionnaires to capture healthcare and non-health resource implications attributable to the ACYP’s autism. *Specific questions were included in resource use form at 20 weeks to assess any adverse events – 20 weeks only.	All *20 weeks only
	Bespoke questionnaire to assess acceptability of the intervention structured around the Theoretical Framework of Acceptability (Sekhon et al., 2017). 11 items, higher scores indicate greater acceptability.	Intervention arm and 20 weeks only.
	Bespoke demographic information form collecting demographic information pertaining to the ACYP and the parent/guardian.	Baseline only

SSIS: social skills improvement system; SDQ: Strengths and Difficulties Questionnaire; CHU-9D: Child health utility 9D; SCQ: Social Communication Questionnaire; ACYP: Autistic children and young people.