"Given the current economic climate, in order to invest in quality teaching, the Government has had to make some trade-offs," Ms Parata said.
Te Kahui Mana Ririki, a child advocacy organisation, welcomed the move.
Director Anton Blank said Maori children in immersion schools would get the attention that they needed.
"It's also supporting kaupapa Maori education, which we know is very successful with Maori kids," he said.
Opposition parties criticised the announcement, with NZ First leader Winston Peters saying smaller class sizes were the best way to raise student achievement and the immunity of Maori immersion schools was unfair.
"This move demonstrates either there's discrimination in favour of one racial group, or the theory that small class sizes are important for education."
Labour's education spokeswoman, Nanaia Mahuta, said: "It's further evidence that smaller class sizes in those kura work well for Maori students, so why not for all students."
Dr Sharples also announced that the Government would spend $76.4 million over four years to improve Maori students' results.
Read all of nzherald.co.nz's Budget coverage here.