A Levin dad who grew cannabis to pay for special tuition to address his child's learning difficulties says he has done his time but his devotion paid dividends - securing his son a better chance at life than he has had.

Graeme and Zef Sowman both live with a learning disorder which inhibits their ability to translate their thoughts to paper.

One got the help he needed - the other did not. The elder Sowman wishes to share their story to encourage parents to recognise the learning difficulties that could shape their children's lives.

"Your child could be the next Albert Einstein. Do you want to be responsible for him never finding out?"

Sowman left school early and set about working hard - first as a cleaner and then a truck driver. He knew there was something different about his son too. As a child Zef once took apart the dying family computer and fixed it.

But the 12-year-old was struggling at school, and Sowman and his former partner sought a diagnosis.

They heard that he was reading and writing at a level of a child half his age, and turned to Palmerston North's special tuition service SpelADD for support.

When he was put into the lowest streamed class at school, Sowman stormed into the principal's office and demanded that his son be accelerated in the top class.

Before long, Zef's results had elevated him to among the top pupils in his year, which Sowman attributes to SpelADD's guidance. He toiled 70 hours a week to continue paying the $100 weekly fees until a trucking accident in 2005 put him out of work.

Faced with the bill and struggling in the jobs market as his learning issues mean he is suited to physical work, Sowman stretched his savings to the hilt - but it wasn't enough.

"It was a pretty desperate situation because I didn't want my son to end up being like me - struggling all his life to get a decent hourly rate."

So Sowman turned to an illicit means of funding his son's education, and in 2009 he paid the price.

"In a way you could call me a career criminal. I went to jail for growing pot . . . I'm going to be judged, anyway - whether I did the right thing with that money or not. If I was a lady I would have become a prostitute if I could have helped fund my child's learning difficulties. Blimey, everybody's got to find a way to make ends meet, and there isn't enough work out there for everybody any more."

SpelADD's Rachel Brandon estimated that for the cost of the two years Sowman spent in prison, the taxpayer could have funded the tuition of 150 children with learning disorders.

"People do turn to crime when their learning difficulties have not been addressed. These people will become desperate and are over-represented in prison statistics and there are a few reasons for that - one is they just don't have employability."

Zef Sowman left school in year 12 to study engineering. Now 22, he works as a corporate training manager. "He's had to work hard to get where he's got now . . . I'm so proud of him for that, because he didn't give up," Sowman said.