Zimbabwe-leaked examination papers to be re-taken!!

The Zimbabwe Schools Examination Council has announced that all the leaked examinations papers are going to be re-taken on the dates due to be announced end of this week. The ordinary level English papers one and two and mathematics papers one and two were leaked at a school in Midlands Province called Whata Secondary school in lower Gweru. Six people were arrested, the school headmaster, 4 teachers and a cook at the school.
According to the ZIMSEC board chairperson professor Levy Nyagura, "Replacement papers are now being set and will be distributed to all Examination cenres so that the Examinations is taken before schools close for the third term. The timetable for the replacement papers will be distributed to Examination centres week ending 14 November 2014."
I have a question here. Why is that the Examination papers are leaking every year? Anyway alas to those who are going to re-take the exams.
Just passing by zebra crossing.