The $5m teen firestarter

Principal Alan Liddle said the damage was 'devastating'. Photo / Sarah Ivey

A teenager has been sentenced to jail for lighting a fire that caused $5 million damage to his high school - a sentence that his lawyer describes as "ridiculous".

"I am just frustrated with this judge ... it's not the first time I have had to go to the High Court [to appeal the sentence]," said lawyer Tony Balme. "He doesn't like home detention and he likes sending youths to prison."

James Harris, 15, set fire to a rubbish bin about 4am on Easter Sunday - a fire that soon erupted into a massive blaze that destroyed Te Puke High School's technical block, including seven classrooms.

In the Tauranga District Court last week, Harris was sentenced to two years in prison by Judge Thomas Ingram, although he was released on bail pending Balme's appeal.

The fire left Te Puke High students - who lost months of work in the blaze and are still in temporary facilities - in despair. "I was devastated, absolutely devastated," said principal Alan Liddle, who described the process for staff as "akin to grieving".

He said Harris was an average student, who, apart from a couple of minor attendance issues, hadn't come to teachers' attention before this. "Which is why it was such a shock."

He said Harris had apologised in person and by letter.

According to police, Harris had been drinking at an associate's house on the evening of Saturday April 11, and had made several visits to a nearby park and the high school through the night.

On one visit, he used gun powder to set fire to a picnic table and a slide in a children's play area. Later, he went to the school grounds and lit a fire in a rubbish bin next to the music room. Associates extinguished that fire.

Around 4am, he returned to the school and started a fire in another bin on a wooden deck attached to the technical block. The bin melted and the fire quickly spread, razing the technical block.

Balme said Harris was "basically showing off".

"He set the fire in a rubbish bin and leaves it smoking ... the rubbish bin burns through and then the building catches on fire and burns down and causes this colossal damage.

"It's a bit different to your run-of-the-mill school fire where you go out with petrol and deliberately burn down the school building. This kid just set a rubbish bin on fire and wandered off."

Balme said it wasn't the first case he had heard of. "It seems rubbish bin fires [are] a popular pastime in Tauranga and Mt Manganui. One kid burnt down a block at a Welcome Bay primary school you know, exactly the same thing, just a fire in a rubbish bin."

Balme said he had told the judge "the building isn't salvageable, but at least this kid can be".

Harris' father Nathan Smith said: "Obviously we are are absolutely shocked and devastated about what's happened.

"We are really taken back by the harshness of the sentence - no doubt about that.

"It's been a real shock to the system, I can tell you. It was very much out of character. James has had some very small issues in the past but this was definitely totally out of character."

Crown prosecutor Hayley Derrick submitted to the district court that the starting point for sentence was four and a half to five years' imprisonment before taking into account aggravating and mitigating factors. She said aggravating features were that less than 24 hours earlier, Harris had started other fires.

Derrick said as well as the replacement costs, there was also extensive personal loss to students, teachers and the wider community.

That included teaching resources, NCEA assessment materials and students' projects. Some students had to repeat their NCEA work.

Liddle did not want to comment on the prison sentence. "His lawyer has appealed the sentence so we need to wait and see. But in all of these tragic events there are no winners."