Introduction:
Despite the evidence of the adverse health effects of smoking, more than one in five adolescents in Europe still smokes in 2015. In order to reduce this high smoking rate, tobacco control policies have been put in place, including school tobacco policies (STPs). The few studies that assessed the equity impact of tobacco control policies, showed either a negative or a neutral effect on equity across socio-economic status (SES), and only one study on STPs addressed smoking inequalities. Therefore, our aim is to determine whether STPs are equally effective, first, among adolescents of different SES groups within a school, and second, across different schools, according to the school SES status.

Methods:
A cross-repeated study was carried out in 2013 and in 2016 in 38 schools from six European countries. A questionnaire was completed by 18,500 adolescents from 3rd and 4th grades and another one by school staff members. We conducted multilevel logistic regression analyses to estimate the effects of STPs on various smoking-related outcomes and stratified by SES. School was used as random effect and we controlled for age and parental smoking.

Results:
A higher score of STP was associated with lower odds of smoking on school premises for both SES groups. However, STP was not associated with smoking just outside school premises, nor with smoking intention. Among low SES adolescents, a higher score of STP was associated with lower odds of being a weekly smoker. A higher score of STP was associated with lower odds of smoking on school premises among both high SES schools and low SES schools. STP was not associated with smoking just outside school premises, expect in high SES schools, where a higher score of STP lead to higher odds of smoking just outside school premises.

Conclusions:
Gaining understanding of who is affected by STPs is important in order to protect the most vulnerable groups.