Some parents are worried their children will not get enough attention in larger-sized classes announced yesterday.
And education experts say the move is unfair to students and teachers.
Education Minister Hekia Parata yesterday said a total of $511.9 million would be allocated to education in this year's Budget, which will be announced next week.
Of that money, $60 million will go towards boosting recruitment and training of new teachers over the next four years.
A postgraduate qualification is also to be introduced as a minimum requirement for all trainee teachers, and would-be school heads will have to gain a pre-principalship qualification.
However, it was Ms Parata's announcement that there would be changes to student-teacher ratios - in one case, up to five extra students in a class - that has upset parents, teachers and others in the education sector.
The new standardised ratio for Years 2 to 10 is will be 27.5 students per teacher. The ratio for Years 2 to 3 is now 23 students per teacher.
The Year 1 ratio of 15 students per teacher will remain the same, while Years 11 to 13 will be standardised to 17.3 students per teacher.
Schools ultimately manage how many students will be in a class, but the ministry's ratios act as a standard.
NZ Principals' Federation president Paul Drummond said the move would result in students missing out on extra one-on-one time and a bigger workload for the teacher.
"The class size debate and the research is unequivocal - smaller class sizes benefit students and are better for them.
"As a teacher, if you could have 20 kids, that was great. It's going to personalise the class and have a more focused programme, rather than having 30 kids."
Mr Drummond, who has been an educator for 30 years, said parents understood that having a smaller class meant their child would get more teaching attention.
"The most common question parents ask when their child starts school is 'how big is my child's class?'."
Some parents were last night concerned about the ratio changes.
Mother of three Kathy Ewen was particularly worried about howchildren with learning disabilities would be affected by being in a bigger class.
"My son is a dyslexic learner ... and we've had to pay for a teacher aid to help him because he can't get the quality of education he deserves.
"It will be the [children] that aren't academic that will get left behind because teachers are spread so far as it is."
Mrs Ewen, whose three children are 11, 13 and 16, said the standard of learning at lower levels would also suffer.
"It's about the kids ... who will probably suffer from such big classes. They should pay teachers more if they do that."
Psychologist Jane Douglas said the ratios were "not a good thing".
"My mother is a teacher and I know the ratios are very important for learning. I think children, especially those who are more intelligent or less intelligent and need more attention, will get left behind."
Ms Parata said the changes would free around $43 million, on average, in each of the next four years.
"About 90 per cent of schools will gain or have a net loss of less than one full-time teacher equivalent as a result of the combined effect of the ratio changes and projected roll growth.
"These more consistent ratios will give schools greater certainty over their resourcing from year to year."
Late last year, the Post Primary Teachers' Association said class sizes varied from school to school but that a survey had found one class had 51 students.
PPTA president Robin Duff, who was a teacher for 38 years, said the idea that a "quality teacher" should be able to handle any size class was flawed.
The president of the NZ Educational Institute, Ian Leckie, said parents needed to be worried about the changes.
"It will affect their child's learning, the school and teachers. Ninety per cent of schools will be affected - there will be teachers lost and even one teacher lost is a bad thing for a school.
"There's absolutely no benefit at all in having a larger class."
Education Minister Hekia Parata said the changes were critical in helping to increase productivity.
"These more consistent ratios will give schools greater certainty over their resourcing from year to year," she said
The changes would free just over $43 million, on average, in each, which would be put back into education.
School Trustees Association president Lorraine Kerr said class sizes were not the issue. Rather, it was the quality of the teacher.
"We believe the quality of a teacher is far more important than the class size - that's the priority. You could have a quality teacher in front of 30 kids and they would be great. In the same way, you could have a class of five and the teacher could be terrible at managing them."
On the Herald's Facebook page, Daniel Eisenhut wrote: "I grew up in classes with more than 30 on the roll; am I less educated than the next ?"
Alexander Forgie wrote that the changes were positive because class sizes would be standardised.
And Joelle Walker wrote: "If the teacher is on the level and has the kids engaged and motivated, class size will not matter."
If you spoke to each child, in a class of 30 children, you would speak to each person for only two minutes.
Bigger classes means less focused time with students, helping those who are particularly struggling and not being able to fully challenge those students who are ahead, says Principals' Federation president Paul Drummond.
"Class size absolutely makes a big difference. If you're a teacher with a smaller class, you're able to deal with a more personalised programme."
Mr Drummond said teachers were expected to cater to the needs of all children, but to also focus on those struggling and those who may need more of a challenge.
"That's going to be difficult if you've got 30 kids to manage - the bigger the class, the harder it is to manage."
PPTA president Robin Duff said bigger classes sometimes meant some children were ignored.
"I like to put it this way, there's 60 minutes in a period and if you spoke to each child, in a class of 30 children, you would speak to each person for only two minutes."
Mr Drummond did not think there were any benefits in bigger classes.