Aims: In 2007, Finnish authorities gave a national recommendation that schools should not sell sweet products. This study aimed to determine the effects of the national recommendation on school-level intermediary determinants (factors related to oral health inequalities) and if the changes were different according to school-level socio-economic position (SEP).

Methods: This ecological and longitudinal study combined school-level data from two independent studies from Finnish upper comprehensive schools (N = 970): the School Health Promotion study (SHPS) and the School Sweet Selling survey (SSSS). The baseline data (SHPS from 2006–2007 and SSSS from 2007) and the post-intervention data (SHPS and SSSS from 2008–2009) were combined into a longitudinal school-level data set (n = 360 and response rate = 37%). The intermediary determinants were: attitudes and access to intoxicants, school health services, school environment, home environment, schools’ health-promoting actions (including sweet product selling) and pupils’ eating habits. Three equal-sized school-level SEP group — slow, middle and high — were formed. The changes in the intermediary determinants were analysed using Wilcoxon Signed Ranks test. Differences between school SEP groups were analysed the using Kruskal–Wallis test. Longitudinal linear mixed modelling was used to determine the contribution of intermediary determinants to the changes in pupils’ eating habits.

Results: The national recommendation was effective in decreasing sweet product selling at schools and the effect was equal in each school-level SEP group. Intermediary determinants contributed differently to eating habits in the three SEP groups.

Conclusions: A national recommendation seems to be an effective tool in making the school environment healthier without increasing inequalities.