Mr McClean, who worked in the tech industry before becoming a teacher, said this was the first year the class had run, after a smaller pilot last year.
There were already 106 applications by those hoping to get on to the course next year.
Students come to school hours before the first bell to work on their projects, as well as on weekends and during the holidays.
"They won't leave. That's the problem for me," Mr McClean said.
"I have basically written-off the holidays."
Baobin Deng, 17, did not know how to code when he began the class this year, but has now nearly finished his app, which counted towards his NCEA Level 3.
It enables diners to order through a large touch screen device on a restaurant table.
They can customise orders quickly by clicking titles, with the system calculating costs and sending an order to the kitchen. Diners can access Facebook, inbuilt games and browse the internet while waiting for their food.
Coding has been called the "new literacy" because of its role in powering our digital world. Websites, apps, computer programmes and everyday objects like microwaves rely on code to operate.
Put simply, it is telling a computer what you want it to do by typing step-by-step commands..
This month an overhauled computing curriculum was introduced in England, with all primary school children learning about algorithms and computational thinking.
The Government here is reviewing how it supports digital technology in the classroom.
"The review brings together a whole range of experts to look at how we strengthen kids' learning of digital technology and covers the curriculum at all levels," Education Minister Hekia Parata said.
"It's a great opportunity to focus on science and technology and make sure we have the right competencies at all year levels.
"We want it to be fit for the future as we move further into the 21st century."
Avondale principal Brent Lewis said technological change meant "by the time the curriculum is written the market has moved on".
For that reason, the school focuses on IT projects.
"Coding is critical, but, really, do you want to study coding with no context? That's tedious, it would drive you nuts. But if you know why you are doing it ... bring it on."
Read more: Cracking the code