"It gives me a first-hand insight into the children and their experiences," he said.
"My job is to explain to the public of New Zealand what the lives of children are like.
"Poverty and inequality is now the leading concern of adult New Zealanders - there is a high understanding of the impact of poverty and violence on children.
"That gives government a mandate to invest to change that. That is a good thing."
New Zealand children desperately need change. He said the country has the highest rate of referral to its child protection agency in the world.
Every year one in every 11 children up to the age 17 - 9 per cent - will be referred to Child Youth and Family (CYF).
Of those 90,000 individuals, 60 per cent have been referred an average of four-and-a-half times.
"That's called churn - kids are going back and back and back, and not getting sorted," he said.
"When you look at the outcomes for kids who have been in care, 80 per cent leave school without NCEA Level 2 - 80 per cent compared to a third of kids who have no care protection history."
One third in protection end up in the youth justice system and are over-represented in prisons.
Of children in care, Maori are 60 per cent and of those in youth justice Maori are 71 per cent.
He said the vast majority of referrals were children who witnessed domestic violence.
"What we are not doing is effectively addressing the parents' violence. That is the big chunk of it."
He famously declared CYF was "broken" but said it had since improved after monitoring.
While it had improved its practices, the agency was swamped. CYF caseloads were "double what they should be".
"They are just too busy - there isn't enough time in a social worker's day to spend time with families.
"They rush from crisis to crisis to crisis, put a bandaid on, make it safe and move on. That is a big part of the problem."
The services that supported CYF were also "working their tails off" and under-resourced.
"Everyone is stretched and there is also a skills gap. As the complexity of families has grown, the development and support of the workforce hasn't kept up. We now routinely have children who are severely damaged - developmentally delayed, highly disordered behaviour - with parents who have intractable long-standing violence, mental illness and addictions."
He said it was "too hard" for services to share information thanks to overly conservative interpretations of privacy laws "that have scared people off" sharing "vital" information about families "in order to understand the situation and effect change".
"It is slowly changing - we have a much clearer direction from the Privacy Commissioner that has been very helpful. Information sharing is improving."
Agencies needed to develop "child-centred thinking".
"The adults talk to each other and we don't spend enough time talking to the child, finding out what they want and need, and what their experience is," he said.
"That really matters. For example in our monitoring we talk to children that have been moved from their parents' care and the siblings are all placed in different houses. They haven't seen each other for months, for no good reason. When you ask the kids what they want, they say 'I want to see my brothers and sisters'.
"Often plans are made without explaining the plans to the kids, or the plans change - they thought they were going home for Christmas and now they are not, and there is no explanation for that.
"So it's not surprising they are very damaged, traumatised kids - their behaviour goes off.
"This is really basic stuff and we see it again and again and again. If you don't ask the kids what they want - these are very damaged kids - their behaviour escalates."
He is Ngati Kahungunu, a handy thing for a Hawke's Bay community paediatrician.
"For the Maori kids their culture really matters to them, knowing where their whanau, iwi and marae is - their whakapapa really matters.
"When you talk to the kids they say, 'I want to know who I am. I want to belong. Where do I belong? Who do I belong to?'
"Not knowing is really important to them. When you talk of the whanau, the iwi and its richness and the great things that have happened, a fantastic marae and a beautiful wharenui, it gives them a sense of pride of identity and a sense of belonging. This we don't prioritise nearly enough."
He said some children's parents had a selective interpretation of what it meant to be Maori, with an emphasis on "being a warrior".
"They have this distorted and wrong view of what it means to be Maori. When you sit down and explain, or talk about someone famous from the iwi and some of the great stories, it gives them a sense of identity and peace.
"It means you have a connection with that younger person that is based on good things. The way we effect change for these kids and help them to heal is through the connection we make with them."
He credits his "immensely talented, hardworking and focused" staff for the success of his five-year role as Commissioner, with $2 billion of focused spending and 35 of 78 recommendations from the expert advisory group to Government either fully or partially implemented, an "extraordinary" number "given that it was commissioned independently of Government and has no authority".
"You never make a difference on your own - it is all about the team," he said.
"Through their work, poverty and inequality is now a leading concern of New Zealanders when randomly polled."
He said alleviating child poverty would have widespread impact. Hospitals were seeing 42,000 cases associated with crowding, poverty and cold/damp houses annually, resulting in 15 deaths in the last year "and the numbers are going up".
"Houses that are insulated properly - floor, ceiling and walls - and where drafts are blocked and have adequate ventilation and heating are warm and dry. We hardly ever see children with these illnesses from houses that are warm and dry."
Some families were spending 70 per cent of household income on rent.
"That is unaffordable so families move in together. We regularly see 10 to 13 people in a house.
"So when you go to the homes you find furniture is pushed out and the lounge is just mattresses." With heating unaffordable, people slept en masse in the lounge and disease "rips through the house and the baby gets sick".
He said Hawke's Bay had the fifth-poorest population of children in the country, with just over half born into the two lowest deciles.
Teachers have told him that about a third of 5 year olds arrived at school with the language ability of between age 3 and 3-and-a-half.
"If you arrive at school age 5 with the language of 3-and-a-half, the likelihood of catching up and getting NCEA Level 2 is very small, probably because the damage has been done, in terms of neural pathways.
"They are language-poor environments, they are highly stressed environments and those kids are arriving at school aged 5 and are not ready to learn. They don't have the social, emotional or cognitive skills they need at 5 to learn."
"A huge amount of work goes on at those low-decile schools to develop those skills, but even in the best schools when you have children that are highly stressed, crowded, in language-poor environments where parents are poorly supported, then outcomes are predictably bad."
A recent low point in his career was the prolonged death of Moko Rangitoheriri at the hands of caregivers.
A high point was the Government's declaration to tackle child poverty.
"I'm naturally impatient and would like change to be faster, but there are very real constraints on officials in government, there are big demands on the public purse.
"It is my job to put the case of the public and explain how our children are doing. We like to believe New Zealand's are great place to be a child, and probably for 70 to 80 per cent of children that is true.
"But for the 20 to 30 per cent of children it is not true. It used to be how well you did was dependent on your talents and your hard work, not the family or income bracket you were born into.
"Nowadays we know that how well you do is highly dependent on the income bracket and neighbourhood you were born into, and that is not right. It is not who we are. It is an immense waste of talent and potential. I don't think that's the country that New Zealanders want."
He said a clear pathway was the Government implementation of all 78 recommendations from the expert advisory group in similar fashion to issues such as employment and immunisation.
"All those things have plans, accountabilities, targets and investment to scale. Not over-investment but just enough to do it properly, then we know those things all can change. We can get our child poverty rate down by more than half, back to where it was when we were kids, if we choose to have that plan, those targets, hold officials accountable and invest wisely.
"The kids would be better off and we would all be better off. The long-term costs of failing to address those issues, like the health costs and mental health costs and justice costs, are unnecessary."
Having lifted public opinion on childhood suffering and giving the Government a political will to act, it is fitting that his successor will be former Youth Court judge Andrew Becroft. "Someone of Andrew's capability and stature in the role, responsible for monitoring Child Youth and Family - I couldn't ask for more."
When interviewed by Hawke's Bay Today, Dr Wills had a persistent light cough. "I'm a bit tired, I think."
