This study aimed to assess the clinical oral health outcome effects among schoolchildren participating in a school-based oral health education (OHE) programme. Local social, cultural and environmental conditions were determinants of the school-based OHE programme, which was compiled on the basis of prevailing beliefs and on what teachers and educational authorities considered to be important for the oral health of schoolchildren. Consequently, the practical aspects of oral hygiene and information on the cause and prevention of caries and gingivitis were the components of oral health education. The teachers were prepared to carry out weekly supervised toothbrushing sessions and monthly lessons on aspects of oral health for the school year in grade 4. Eight participating schools were selected for the clinical effect evaluation and four non-participating schools served as the control. In total, 309 children from the participating schools and 122 children from the non-participating schools were available for the evaluation. Their ages varied between 9 and 14 years. The mean plaque score, calculus score and gingival bleeding score at baseline and at follow-up examinations 3, 8, 15 and 36 months later were not significantly different for participating schools and controls. The mean DMFT value at baseline was 0.4 and 3 years later 0.9 in both the participating and control schools. In conclusion, the present study shows that the implemented school-based OHE programme did not result in significant reductions of the clinical parameters measured.