Education spokespeople from both the Labour and National parties say the special education system needs improving.
Speaking on Radio New Zealand's Nine to Noon programme today, National's Hekia Parata and Labour's Chris Hipkins, said some children are missing out on support.
Ms Parata said the government has improved special education, but there is more to do.
Chris Hipkins said the area is a ticking time bomb.
The pair also debated their big-ticket education policies worth about $350 million over the next four years.
Ms Parata said her party's plan of using the money to pay teachers to work in groups of schools is on track despite opposition from half the primary school workforce.
"Schools are expressing their interest, and that includes primary schools, and I was in Balclutha and Gore on Friday, and they're interested for instance. I was in Taranaki two days before that and they're interested."
Labour will spend the money on more teachers and Mr Hipkins said that will help children who are not doing well.
"There's really good research that shows smaller class sizes have a particularly positive impact for kids who are falling behind, because teachers do have extra one-on-one time with them," he said.
Mr Hipkins said poverty is harming many children's performance at school.