Table 1

Baseline characteristics of schools and students by trial arm and overall

School (cluster) characteristicsSBMT armTAU armTotal
n=43n=41n=84
Region
 England, n (%)38 (88)36 (88)74 (88)
 Scotland, n (%)2 (5)1 (2)3 (4)
 Wales, n (%)1 (2)2 (5)3 (4)
 Northern Ireland, n (%)2 (5)2 (5)4 (5)
School size—at least 1000 students, n (%)20 (47)22 (54)42 (50)
Type of school
 Mixed, n (%)36 (84)37 (90)73 (87)
 Girls, n (%)7 (16)4 (10)11 (13)
School quality rating
 Requires improvement, n (%)6 (14)5 (12)11 (13)
 Does not require improvement, n (%)37 (86)36 (88)73 (87)
Deprivation
 Above median percentage eligible for free school meals, n (%)15 (35)15 (37)30 (36)
 Below median percentage eligible for free school meals, n (%)28 (65)26 (63)54 (64)
Provision of Social Emotional Learning, mean (SD)12 (2.5)12 (2.6)12 (2.6)
Student characteristicsSBMT armTAU armTotal
n=4232n=4144n=8376
Gender
 Female, n (%)2350 (56.5)2159 (53.1)4509 (54.9)
 Male, n (%)1724 (41.5)1823 (44.9)3547 (43.2)
 Other, n (%)14 (0.3)12 (0.3)26 (0.3)
 Prefer not to say, n (%)69 (1.7)69 (1.7)138 (1.7)
Ethnicity—white, n (%)3237 (78.1)2965 (73.2)6202 (75.7)
Age, mean (SD)12.2 (0.6)12.2 (0.6)12.2 (0.6)
Year group
 Year 7, n (%)2082 (49.2)2142 (51.7)4224 (50.4)
 Year 8, n (%)1878 (44.4)1827 (44.1)3705 (44.2)
 Year 9, n (%)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 and behavioural functioning (SDQ) total difficulties—self report, 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 are provided for all 43 schools in the intervention arm and 41 of the 42 schools in the control arm (1 school withdrew soon after randomisation). No all boys schools were recruited.

  • Sample size ranges from 4145 to 4232 students in the intervention arm and 4048 to 4144 students in the control arm. In the intervention arm, 4157 students provided data on gender, 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, 4048 students provided data on ethnicity, 4140 students provided data on CES-D, 4081 on SDQ and 4119 on WEMWBS. Age and year group data are available for all students.

  • School year groups correspond across the home nations as follows: England 7, 8, 9 and 10; Northern Ireland Years 8, 9, 10 and 11; Scotland S1, S2 and S3.

  • CES-D, Center for Epidemiologic Studies for Depression Scale; SBMT, school-based mindfulness training; SDQ, Strengths and Difficulties Questionnaire; TAU, teaching as usual ; WEMWBS, Warwick-Edinburgh Mental Well-being Scale.