Table 1.

Progression criteria

Progression criteria		Outcome
1	Recruitment of an average of 48 pupils per year group from the schools included in the pilot phase (48 being 80% of the target average recruitment of 60 pupils per year group)	Achieved, some study modifications planned
2	Confirmation of the feasibility of the outcome data collection methods and time points within the school year	Achieved, some study modifications planned
3	Minimum of 80% response rate to questionnaires at follow-up	Partially achieved, some study modifications planned
4	Assessment of contamination in the control group and whether feasible and more efficient to continue randomisation within schools (by year group) or switch to randomisation at the school level in the main phase of the trial and calculation therefore of the required number of schools	Within-school randomisation was feasible. Sample size recalculated
5	Agreement to participate in principle obtained from 80% of the number of schools required for the main trial (based on 4)	Achieved
6	Confirmation of feasibility of embedding the education component within the curriculum	Achieved
7	An indication of a positive effect of the intervention on self-reported frequency of tooth brushing, at approximately 12-week follow-up, using a one-sided 80% confidence interval approach	Achieved