New research has found New Zealand teachers had difficulty finding time to teach spelling in a tightly packed day and their initial training did not give them the adequate skills to teach the subject proficiently.
But Mr Oliver said he had no doubts about teachers' abilities to teach the subject.
University of Canterbury senior education lecturer Dr Brigid McNeill said teachers typically used a memory-based strategy - spelling tests with pre-taught words - rather than concentrating on developing skills which would help children spell all words correctly.
"They need to teach children about prefixes and suffixes, to identify sounds within words, and about common spelling patterns in English. If they know how to spell a word such as define and they know the spelling of the suffix tion then they have a good shot at spelling definition correctly."
Dr McNeill surveyed 405 primary school teachers from a variety of regions and schools of varying socio-economic status on their spelling instruction and assessment practices.
There was a large variation in practices, but most teachers focused on development through analysing spelling errors.
Teachers struggled to find time to teach spelling within the curriculum and lacked professional knowledge about English language structure.
"Many teachers also reported that their initial teacher education programmes did not provide them with adequate training in this area."
Dr McNeill said teachers needed to build their language structure awareness so they could provide explicit instruction in spelling.
Working on language structure awareness not only benefited spelling, but also vocabulary development and reading skills, she said.
New Zealand children were struggling more with writing than reading - with 32 per cent performing below national standards.
Although spelling was only one component of writing development, accurate and fluent spellers had more cognitive resources to focus on higher-order aspects of writing, Dr McNeill said.
Meanwhile, an international survey in which New Zealand 9-year-olds finished last-equal in maths among peers in developed countries has raised the concern of Education Minister Hekia Parata.
Almost half could not add 218 and 191 in a test and the problem persisted into high school, where there were still students who struggled with the basics.
Ms Parata described the Trends in International Mathematics and Science Study results as "extremely concerning", especially for a government that wanted to get more students into maths-centred professions such as information technology and engineering. APNZ
