Learning support co-ordinator jobs have not been allocated fairly, some principals say.
The government has chosen just over 1000 schools to get the first of the 623 jobs it is creating.
Schools deemed to have an advanced use of working with the Learning Support Delivery Model have been prioritised.
But New Zealand Principals' Federation president Whetu Cormick said that was a surprise.
"We understood that the first tranche of these positions would be allocated fairly and evenly across the board but what we've found is that there seems to be a bias towards the established communities of learning."
Mr Cormick said a lot of schools with great need had missed out.
"It is a concern and many, many principals - 1500 in fact - are absolutely disappointed and in some instances gutted that they've been left out at this time."
But Associate Education Minister Tracey Martin said she had always signalled that those co-ordinators would be going to schools using the model.
"There were always going to be some who did not receive a learning support co-ordinator in the first tranche.
"However, every school in New Zealand can be moving into or changing the way they deliver learning support by participating in the Learning Support Delivery model."
She said schools that had need but unable to implement the model should get in touch.
Budget 2019 included an extra $217 million of operating funding over four years to cover the cost of the new positions.