Table 1.

Results of methodological assessment of studies included in the review

	Number of studies in each assessment category*
Criteria	Y	S	N	NC	NR	PR	NA	NP	P
Did the study address a clearly focused issue?	15
Was/were the study outcome(s) to be measured clearly described?	15
Were the questions posed to assess outcome(s) clearly defined?	14		1
Was the study samle clearly defined?	13								2
Were participating schools recruited in an acceptable way?	4	1		1			1	8
Were the pupils recruited in an acceptable way? 1	11			4
Were characteristics of subjects at enrolment reported?	12		1						2
Is it clear how data were collected?	15
Did the authors mention that the instrument used for data collection was pre-tested or validated?	8		6						1
Were the questions posed appropriate to address given outcomes?	10			1				4
Was participation rate reported?	9			2	4
Was participation rate sufficiently high?	7	1	1					6
Was the data analysis sufficiently rigorous?	15
Were other factors accounted for that could affect outcomes?2	15
Were results appropriately reported? 3	11	1							3
Is there a clear statement of findings?	15

*Y = Yes, S = Substandard, N = No, NC = Not Clear, NR = Not Reported, PR = Partially Reported, NA = Not Applicable, NP = Not Possible to Assess, P = Partly

¹ did all pupils at the school(s), respectively in the grade concerned, have the same chance to participate?

² for example, sex, age, grade, school type, social class

³ were numbers of outcome events reported on?