"For that to happen effectively, smaller class sizes are beneficial because you're having a lot more one on one interaction."
Hiring extra teachers would also make a difference as long as they were effective teachers, he said.
Mr Murfitt said funding digital devices was a positive move.
A Labour government would provide a $100 subsidy towards buying tablets or netbooks, with parents paying off the remainder at $3.50 a week.
The poorest families could call on a $5 million hardship fund to assist if they cannot afford payments or fall into arrears.
"It's about equity and there are many students [whose] families can't afford [digital devices], and in many places you're getting those who have and those who haven't," he said.
Devices were "becoming a norm" in the classroom.
"I believe as a country we need to support all students to access the norm," Mr Murfitt said.
Education Minister Hekia Parata said it was unnecessary to reduce class sizes, and last time a Labour government introduced the policy it made little difference to student achievement.
However, Labour's policies have found favour with teacher unions and education groups.
New Zealand Educational Institute president Judith Nowotarski said yesterday Labour's plan to introduce a more rigorous pre-screening programme for teacher education would go a long way to ensuring the "best and brightest" entered the profession.
"In recent years there has been virtually no oversight of teacher training and this has led to too many courses, too many students and not enough emphasis on quality."
Labour's policy was a welcome shift from National's policy of "dumbing down" the teaching profession by allowing unqualified and unregistered people into charter schools and early childhood education, she said.