Pompallier Catholic College principal Richard Stanton said the changes would disadvantage this year's NCEA students.
"Instead of having four weeks at school in term four to work towards external exams, students will have only eight school days," he said.
"This is far from an ideal learning situation for students sitting exams and may detract from our usual excellent results."
Kamo High School principal Bernie Taffs agreed, saying his students had only 21 days of teaching left before NCEA exams began. "It's about making sure in the next couple of weeks they've got a good plan going forward."
Tauraroa Area School principal Grant Burns said his students had only 19 days of pre-NCEA teaching left.
"It's certainly not an advantage and it's making things more difficult. It remains to be seen if it will be seen in marks," he said. "The games themselves are another distraction, but not every kid is an avid rugby follower."
Mr Burns said the Rugby World Cup was just one more distraction which students needed to contend with. "On the positive side, students have shown a real interest in learning about the countries that are playing and most schools are using the opportunity to engage students."
Mr Stanton agreed, saying the cup had lifted the spirit of the community and enabled students "to participate in many areas".
"Two of our students carried flags at the official welcome, six participated on the sideline and others were volunteers. Members of the Tongan team visited the college."