Berten et al. BMC Public Health 2012, 12:215 http://www.biomedcentral.com/1471-2458/12/215 Table 1 Outcome and control variables by type of education Percentages More than 3 times in the last month beer/wine no yes strong spirits no yes cannabis no yes Gender girls boys Cultural background natives migrants Parents’ educational level no parents with higher education one parent with higher education two parents with higher education Parents’ work status no parents working one parent working two parents working * p < 0.05, ** p < 0.01, *** p < 0.001 79.3 20.7 92.1 7.9 95.8 4.2 52.8 47.2 47.8 52.2 38.5 29.0 32.4 12.9 35.5 51.7 80.3 19.7 88.7 11.3 92.8 7.2 55.6 44.4 42.6 57.4 54.9 28.0 17.1 11.5 44.3 44.3 82.4 17.6 84.9 15.1 88.6 11.4 53.0 47.0 22.6 77.4 67.5 19.3 13.3 24.4 43.5 32.1 general Education type technical vocational Total p (X2) 80.3 19.7 89.6 10.4 93.3 6.7 53.7 46.3 40.2 59.8 49.4 26.7 23.9 14.8 39.7 45.5 n.s. *** *** n.s. *** *** *** Page 4 of 9 compared to general education (12.9%). That students’ education type can’t be isolated from their familial back- ground, becomes even more apparent if we regard dif- ferences in parents’ educational level. The proportion of students living in ‘high-educated families’ is significantly higher in general education (32.4%) than in technical (17.1%) and vocational education (13.3%). For migrant students, we observed a similar trend: vocational educa- tion included the highest percentage of migrant students (77.4%) followed by technical (57.4%) and general educa- tion (52.2%). Gender differences within various educa- tion types were not significant. Education type and substance abuse In general, a fifth of all respondents drunk beer or wine on more than three occasions during the 30 days prior to the survey. This is roughly twice the number of stu- dents who frequently (i.e. more than 3 times) used spir- its (10.4%) and thrice the number of frequent cannabis users (6.7%). Regarding the association between sub- stance use and education type, a significant association was found for spirits and cannabis. Hence, the propor- tion of students who used these substances was signifi- cantly higher in vocational education, respectively 15.1% and 11.4%, than in technical education (respectively 11.3% and 7.2%). General education counts the lowest percentage of frequent strong spirit (7.9%) and cannabis (4.2%) users. These findings are in line with the raised expectation that frequent substance use is more concen- trated among students in lower educational tracks. Multilevel analysis Because cluster sampling methods were used to collect the data and since the dependent variables are dichoto- mous, multilevel logistic regression techniques were used for the multivariate analysis, with the schools as the higher level units of analysis. The models were fitted in each multiple imputed dataset. The obtained coeffi- cients and standard errors were then pooled according to Rubin’s rules [41]. Finally, regular Wald tests are used to evaluate the null-hypotheses that the respective coefficients are equal to zero in the population. In Table 2, results are shown for the analyses on the full sample of 3 rd to 6th year students. Concerning the sociodemographic factors, gender, age and cultural back- ground, were significantly associated with frequent alco- hol and cannabis use. As expected, boys and older students and native students use alcohol and cannabis