Table 1. Characteristics of the analyzed subjects.

	Junior high school		High school
	N	%	N	%
SEX
Boys	19,153	49.7	29,641	49.1
Girls	19,399	50.3	30,674	50.9
Grade
Grade 7 and 10	13,041	33.8	21,444	35.6
Grade 8 and 11	12,816	33.2	20,168	33.4
Grade 9 and 12	12,476	32.4	18,466	30.6
Unknown	219	0.6	237	0.4
Feeling happy/unhappy at school
Happy at school	25,547	66.3	36,976	61.3
Neither happy nor unhappy at school	9,930	25.8	17,191	28.5
Unhappy at school	2,514	6.5	5,174	8.6
Unknown	561	1.5	974	1.6
Intending to study at university
Yes	5,446	14.1	33,845	56.1
No	26,064	66.6	20,358	33.8
Not yet decided	6,403	16.6	5,165	8.6
Unknown	639	1.7	947	1.6
Participating in extracurricular activities
Yes	30,554	79.3	37,842	62.8
No	7,107	18.4	21,422	35.5
Unknown	891	2.3	1,051	1.7
Having breakfast
Everyday	33,975	88.1	49,298	81.7
Sometimes	2,720	7.1	6,039	10.0
Seldom	1,386	3.6	4,136	6.9
Unknown	471	1.2	842	1.4
Bedtimes
Before or at midnight	26,348	68.3	25,457	42.2
After midnight	11,532	29.9	33,876	56.2
Unknown	672	1.8	982	1.6
Smoking (past 30 days)
No	37,729	97.9	56,994	94.5
Yes	756	2.0	3,178	5.3
Unknown	67	0.1	1,439	0.2
Drinking (past 30 days)
No	34,685	90.0	49,353	81.8
Yes	3,484	9.0	10,643	17.7
Unknown	383	1.0	319	0.5
Mental health status
Good	23,448	60.8	28,936	48.0
Poor	14,509	37.6	30,407	50.4
Unknown	595	1.6	972	1.6