Table 1.

Descriptive characteristics of the study sample

	na	%	95% CI
Total	5478	100
Age
Mean (s.d.) in years	15.19 (1.82)		15.03–15.35
Missing	0	0
Sex
Males	2469	52.17	49.70–54.62
Females	3009	47.83	45.38–50.30
Missing	0	0
Grade
7	1126	11.92	9.73–14.52
8	1088	12.55	10.16–15.40
9	815	16.82	15.14–18.64
10	816	17.13	15.56–18.83
11	837	17.76	16.26–19.37
12	796	23.82	21.68–26.10
Missing	0	0
Subjective socioeconomic status
Low	1470	29.09	26.68–31.63
High	4008	70.91	68.37–73.32
Missing	0	0
Ethnicity
White	3205	59.73	55.18–64.12
Black	300	5.43	4.42–6.65
East/SES Asian	510	9.60	7.61–12.05
South Asian	554	9.78	7.54–12.61
Other	877	15.12	12.94–17.59
Missing	32	0.33	0.18–0.62
Physical fighting
Mean (s.d.)	1.18 (0.64)		1.16–1.21
Missing	201	3.67
School bullying victimisation
Mean (s.d.)	1.47 (0.98)		1.42–1.52
Missing	105	1.92
School bullying perpetration
Mean (s.d.)	1.25 (0.69)		1.22–1.29
Missing	104	1.90

^aData are shown as count unless otherwise indicated.