There are concerns increases in teacher student ratios will lead to less teaching of technical subjects, leading to a shortage in the trades.
Changes to teacher student ratios mean many intermediate schools will have to make choices about which teachers will lose their jobs, putting technical experts in woodwork, cooking and sewing on the line.
Green MP Catherine Delahunty says it's important children are able to engage in a diverse range of learning.
She says many children get inspired by technical subjects, allowing them to get interested in the trades.
"The Green party's getting messages from principals and parents saying this is desperate stuff, why didn't they talk to us about how important these tech teachers are, because classroom teachers don't have these skills."
Ms Delahunty says some students aren't academic and rely on these subjects.
"We want to improve the number of people available to work at the trades level and the government does this to them. It's really quite disastrous and what's going to happen is they're going to realise this in time, and have to go back and rebuild a workforce that's been decimated."
The Government last week labelled education as one of the 'big winners' of the Budget.
But news that teacher numbers will be capped as school rolls continue to grow, is infuriating many sector professionals.
Head of Upper Hutt's Fergusson Intermediate School, Paul Patterson, is horrified by what the government's doing to state education.
"I would really hope that the news media would really get Hekia Parata and John Key and Bill English to justify this decision to the public of New Zealand."
Paul Patterson is faced with losing three teachers from his school because of the changes.
It's estimated 1000 teachers could lose their jobs nationwide.
The primary school teachers' union is going to use its concerns about increasing class sizes in its upcoming bargaining with the Government.
The changes to class sizes were announced as part of the Budget.
NZEI president Ian Leckie says negotiations on the renewal of the primary teachers' and primary principals' collective agreements are due to begin in August.
"If the Government are going to announce class size increases through a budget then we will be using this mechanism to get it onto the agenda, to get it reviewed and, we hope, get it reversed."
Mr Leckie says the NZEI will consult with teachers, principals and parents before entering negotiations.
"What we've got to remember is that teachers' working conditions actually are children's learning conditions."
The NZEI says principals, teachers and parents have been contacting them, frustrated at the announcement made in the Budget.
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