New Zealand Qualifications Authority figures released this week showed schools across New Zealand had 53.6% of their pupils achieve NCEA level 3 last year.
Thirteen of 27 Otago schools failed to reach the national average, more than the nine schools which failed to meet or exceed the national average in 2009.
The trend was similar in NCEA level 1. Two schools fell below the national average in 2009, and in 2010 the number increased to three schools.
Otago Secondary Principals' Association chairwoman and Queen's High School principal Julie Anderson said she had not heard any reports from teachers or pupils saying the assessments at level 3 were more difficult than previous years.
Rather, she said the statistical phenomenon might be due to a number of reasons.
"There is sometimes a cyclic nature to school years. You definitely have cohorts of pupils with different strengths going through.
"There are a lot of factors that impact on a school. For instance, a change in emphasis of assessments can have an impact," she said.
Secondary Principals' Association New Zealand executive member and Otago Girls' High School principal Jan Anderson said the downturn in the economy might also be having a significant impact on NCEA statistics.
She said many pupils went in to jobs or apprenticeships instead of staying on in year 13, because they were perhaps less academically able.
However, with the New Zealand economy taking a hammering in the past two years, fewer jobs or apprenticeships were available, and many pupils had decided to stay on at school and have a go at NCEA level 3 while doing Gateway programmes.
NZQA deputy chief executive, qualifications, Bali Haque said schools were different in the way they designed their courses and qualifications for pupils.
"The public should be aware that factors like decile, roll numbers and courses offered, will influence a school's statistics."
He said the statistics were provided by NZQA each year to assist schools and teachers in their planning, and any comparisons between schools should be treated with caution.
An analysis of the statistics was expected to be released some time next week in a publication which is titled NCEA and New Zealand Scholarship Data and Statistics (2010), Mr Haque said.
