the Education Amendment Act 2000 puts in place a new "system for determining enrollment of students in circumstances where a school has reached its roll capacity and needs to avoid overcrowding." Schools which operate enrolment schemes have a geographically defined "home zone". Residence in this zone, or in the school's boarding house, if it has one, gives right of entry to the School. Students who live outside the school's home zone can be admitted, if there are places available, in the following order of priority: special programmes; siblings of currently enrolled students; siblings of past students; children of board employees; all other students. If there are more applications than available places then selection must be through a ballot, which is randomly selected. Critics have suggested that the system is fundamentally unfair as it restricts the choice for parents to choose schools and schools to choose their students. In addition, there is evidence that property values surrounding some more desirable schools become inflated, thus restricting the ability of lowers socio-economic groups to purchase a house in the zone. School qualifications The Government-run student qualification system is the National Certificate of Educational Achievement ("NCEA"). At some schools students can opt for IGCSE/A-levels (popularly known as "Cambridge exams") or the International Baccalaureate Diploma. NCEA has three levels, one for each of the last three years of secondary school. It contains a mix of internal and external assessments. NCEA replaced the old School Certificate, Sixth Form Certificate and Bursary systems. The IGCSE and A-level exams of the Cambridge International Examinations Board are offered at some schools. For these qualifications, IGCSE is sat in year 11, AS-level in year 12 and A-level in year 13. Neither of these independent qualifications are registered on the NZQA National Qualifications Framework. University Entrance, based on NCEA results, allows entrance to New Zealand universities. New Zealand Scholarship is a qualification pitched at students within the top stanine level. Fees and donations Strictly speaking, no fees need to be paid for education at a state school provided the student is a New Zealand citizen or permanent resident, or an Australian citizen. However, most schools also ask for a "voluntary donation" from parents, informally known as "school fees" or a "parental contribution". Trades unions The Post Primary Teachers' Association (PPTA) is the largest trade union in secondary education in New Zealand with 18,000 teaching staff employed in state and state integrated