Cellphones will be banned in schools across New Zealand, conservative Prime Minister Christopher Luxon said Friday, as his fledgling government looks to turn around the country's plummeting literacy rates.

New Zealand's schools once boasted some of the world's best literacy scores, but levels of reading and writing have declined to the point that some researchers fear there is a classroom "crisis".

Luxon declared he would ban phones at schools within his first 100 days in office, adopting a policy trialled with mixed results in the United States, United Kingdom and France.

The move would stop disruptive behaviour and help students focus, Luxon said.

"We are going to ban phones across New Zealand in schools. We want our kids to learn and we want our teachers to teach," he said.

Researchers from New Zealand charity Education Hub warned of a "literacy crisis" in 2022, finding more than one-third of 15-year-olds could barely read or write.

"That something must be done to address the distressingly low literacy rates in Aotearoa New Zealand is clear," they wrote.

Luxon's conservative government, sworn in on Monday, has been mired in controversy during its first week in power.

Doctors warned the country faced a looming public health "tragedy" after the government unexpectedly scrapped world-leading tobacco control measures that aimed to prohibit the sale of cigarettes to anyone born after 2008.

Luxon has also agreed to restart offshore oil and gas exploration, junking one of former premier Jacinda Ardern's signature climate change policies.