Several factors may explain this phenomenon.  One is private tuition.
Indeed, much ground is covered in private tuition during HSC first year with tuition running up to even December during school holidays.
Parents are ready to pay, and students are eager to sacrifice leisure activities, in order to cover as many topics or chapters as possible in preparation for the second year.
A student of Literature in English, for instance, is expected to study eight texts in a span of two years, after which he is able to take part in the final examination.  He covers four texts at school as well as in tuition in Lower Six.  In agreement with the teacher in tuition, he may decide to start working on one or two texts set for the second year.  Thus, during November and December and in some cases the week preceding resumption of studies the following year, he has ample opportunity to prepare a good part of the texts.  He is “en avance”, as we say.
Athol Fugard’s play “The Road to Mecca” is 79 pages long.  Alan Ayckbourn’s play “Absurd Person Singular” is not more than 93 pages.  In two months, quite a bit of ground can thus be covered.
Past Exam Papers
By the time the student reaches June or the third term, he obviously has covered a major part of the syllabus.  He doesn’t have to depend on the school teacher to complete the work as in tuition he has already covered it.
This idea of being “en avance” is a tempting one as it allows the student to feel miles ahead of the school work.  Besides, in tuition, there are past-exam papers to tackle and personal attention involved.
The perception some students may have of school is that it is not much of a help concerning revision or it is not effective enough in raising their standard.  They find that tuition is answering their needs better in terms of critical thinking, writing skills or discussions.  They therefore choose to stay away from school even if it entails losing out on the fees paid by the government.
However, all this is no justification for staying home because it sets a bad example to other stude- nts.  It is for parents to see to it that their children go to school as regularly as possible.  Both parents and students have a responsibility towards school and there is a need to sensitize them about their responsibilities.
Some students may argue that nothing is being done at school and thus there is no point in attending classes.  Parents must not take this kind of argument at face value and accept that their children stay home so as to revise.  They must verify how far it’s true before reaching a decision.  Some students can be very good at playing on the emotions of their parents in order to convince them that what they will do at home is much better than what they will do at school.
As long as students will cover their workload well in advance thanks to tuition and as long as some parents do not face their responsibilities, this problem will come up again and again.
Let us remind parents that one way of preventing the young to fall in bad ways is to see to it that students conform to the rules and attend classes regularly.  
We must not commit the mistake of dissociating absenteeism from the growing problems like drinking, smoking, and drugs among students.