"So that's why you get a high concentration [of kura] in places like Murupara."
He said the higher NCEA achievement rates in Māori-language kura, combined with the new demographic statistics, showed that Māori students learned better in te reo.
"Learning Māori makes you clever, that's what that tells you," he said.
"The long tail in Māori education are monolingual [English-speaking] Māori, mainstream Māori.
"This country is set up to deliver a mainstream colonial education. It was designed for that purpose, the system serves that purpose. So we are bucking the trend."
Only 2.9 per cent of all Māori school-leavers attended Māori-medium schools, and until now it was thought that those students might be largely from better-off Māori families whose parents cared most about education.
The new data is still not conclusive because it relates to all 64,000 Māori parents - 26 per cent of all Māori parents - who had children living with them at the time of the 2013 Census and said they had children who had attended "kaupapa Māori" education at any stage of their lives.
"Kaupapa Māori" education was not defined in the question and parents may have interpreted it widely. Only 18,054 Māori students, or 5.4 per cent of all Māori primary and secondary school students, were actually learning in Māori more than 50 per cent of the time last year.
Nevertheless, the data does suggest that students learning in te reo are likely to live in families that are poorer than average.
Fully 41 per cent of Māori parents who were unemployed at Census time said they had had children in kaupapa Māori education, compared with only 24 per cent of Māori parents who were working fulltime and 23 per cent of those working part-time.
And 28 per cent of Māori parents earning less than $40,000 a year said they had had children in kaupapa Māori education, but only 23 per cent of those earning between $40,000 and $100,000 and 16 per cent of those on over $100,000.
But Bird said Māori-language schools had to cope with a shortage of educational resources in te reo, and he was glad to see non-Māori as well as Māori people now learning the language.
"When I turn on the television and see Pākehā people having a crack at te reo, it warms the cockles of my heart. It sends a signal to me that we matter," he said.
"The ultimate circuit-breaker is education. If we fix up the education system so that it delivers for my people, guess what? The prisons will empty out, the Māori prisons will become a thing of the past."