New Zealand spent US$5573 (NZ$6804) per primary student, lower than the OECD average of US$7153, and US$6994 per secondary student, below the average of US$8972.
"This suggests that our teachers overall do a great job and are cause for celebration not carping criticism," Prof O'Neill said.
He said Treasury also failed to report New Zealand student-teacher ratios were higher than OECD averages.
New Zealand schools have 16.3 primary students per teacher, compared with the average of 16.0, and 16.3 lower secondary students per teacher, compared with the average of 13.5.
Only upper secondary school ratios were better than average, with 12.8 students per teacher, compared with the average of 13.5.
"In other words, our ratios need to be reduced overall to match the OECD average, not further increased," Prof O'Neill said.
Criticisms about the rising costs of schooling were misleading, and increases in Government funding were about catching up on underfunding in past years, he said.
The cost of teacher salaries, divided by the total number of students, was below OECD averages for both primary and secondary schools.
Prof O'Neill said New Zealand teachers appeared to provide very good value for money to the Government and the country.