Table 1.
Baseline characteristics of schools and students by trial arm status and overall
| School (cluster) characteristics | SBMT | TAU | Total |
| K=43 | K=41 | K=84 | |
| Country, n (%) | |||
| England | 38 (88) | 36 (88) | 74 (88) |
| Scotland, n (%) | 2 (5) | 1 (2) | 3 (4) |
| Wales | 1 (2) | 2 (5) | 3 (4) |
| Northern Ireland | 2 (5) | 2 (5) | 4 (5) |
| Urbanity—urban, n (%) | 36 (84) | 35 (85) | 71 (85) |
| School size—at least 1000 students, n (%) | 20 (47) | 22 (54) | 42 (50) |
| Type of school, n (%) | |||
| Mixed | 36 (84) | 37 (90) | 73 (87) |
| Girls | 7 (16) | 4 (10) | 11 (13) |
| School quality rating, n (%) | |||
| Requires improvement | 6 (14) | 5 (12) | 11 (13) |
| Does not require improvement | 37 (86) | 36 (88) | 73 (87) |
| Deprivation | |||
| % eligible for free school meals, mean (SD) | 13.2 (8.1) | 11.8 (10.7) | 12.5 (9.4) |
| Provision of PSHE education, mean (SD) | 12 (2.5) | 12 (2.6) | 12 (2.6) |
| SEL ethos, mean (SD) | 50.0 (9.7) | 49.9 (10.5) | 50.0 (10.1) |
| n=4232 | n=4144 | n=8376 | |
| Gender, n (%) | |||
| Female | 2350 (56.5) | 2159 (53.1) | 4509 (54.9) |
| Male | 1724 (41.5) | 1823 (44.9) | 3547 (43.2) |
| Age, M (SD) | 12.2 (0.6) | 12.2 (0.6) | 12.2 (0.6) |
| Ethnicity—white, n (%) | 3237 (78.1) | 2965 (73.2) | 6202 (75.7) |
| Year group, n (%) | |||
| Year 7 | 2082 (49.2) | 2142 (51.7) | 4224 (50.4) |
| Year 8 | 1878 (44.4) | 1827 (44.1) | 3705 (44.2) |
| Year 9 | 79 (1.9) | 64 (1.5) | 143 (1.7) |
| Year S1, n (%) | 193 (4.6) | 111 (2.7) | 304 (3.6) |
| Depression (CES-D), mean (SD) | 13.6 (10.0) | 13.3 (9.8) | 13.5 (9.9) |
| Social–emotional–behavioural functioning (SDQ), mean (SD) | 11.8 (6.5) | 11.7 (6.4) | 11.8 (6.5) |
| Well-being (WEMWBS), mean (SD) | 49.7 (9.7) | 49.6 (9.7) | 49.7 (9.7) |
Data on baseline characteristics were provided for all 43 schools in the intervention arm, and 41 of the 42 schools in the control arm. Sample size ranges from 4157 to 4232 students in the intervention arm and from 4063 to 4144 students in the control arm. In the intervention arm, 4157 students provided data on gender (83 reported other/prefer not to say); 4145 students provided data on ethnicity; 4230 students provided data on CES-D; 4171 on SDQ; and 4214 on WEMWBS. In the control arm, 4063 students provided data on gender (81 reported other/prefer not to say); 4048 students provided data on ethnicity; 4140 students provided data on CES-D, 4081 on SDQ; and 4119 on WEMWBS. School year groups correspond across the home nations as follows: England and Wales, years 7 and 8 (pupils aged 11–12 and 12–13, respectively); Northern Ireland, years 8 and 9 (pupils aged 11–12 and 12–13, respectively); Scotland S1 (pupils aged 12–13). Age and year group data were available for all students. In SDQ, specifically, the Total Difficulties–Self-report scale was used. For further details of the measures, see online supplemental B.
CES-D, Center for Epidemiological Studies for Depression Scale; PSHE, personal, social, health and economic; SDW, Strengths and Difficulties Questionnaire; SEL ethos, school social–emotional learning ethos; WEMWBS, Warwick-Edinburgh Mental Well-Being Scale.