But by night, he's a YouTube superstar. Eddie Woo is arguably the country's most famous maths teacher.

The 31-year-old's YouTube channel, Wootube, where he posts videos of his maths classes at Cherrybrook High School, has 22,000 subscribers and has clocked up more than 2½ million views.

One of his most popular videos, where he explains the number "e" and what exactly exponential growth is, has had more than 138,000 views and received rave reviews in the comments.

"This guy is just brilliant ... I was speechless. He made maths so fun and interactive, something almost no teacher does," wrote viewer Reeta Singh.

"Wow the lights went on! What a great teacher. I now understand," posted Mary Ann Mehegan.

In his Wootube videos, filmed from the perspective of his students, with their reactions and interjections forming part of the soundtrack, Mr Woo is warm and animated, and so engaged with his subject and committed to his students you'd defy even the most cynical kid to remain unmoved.

"Teaching is a performance; you need to be a presence in the classroom," he said.

Mr Woo didn't set out to teach maths. He preferred drama, English and history when he was a student at James Ruse Agricultural High School, where he finished in the top 2 per cent of the state.

Becoming a teacher was not a popular choice at James Ruse.

"I was the only person in my grade who went into education. It's quite an uncommon thing ... because of our culture and the place of teachers, it's 'why would you do that with all this vast academic potential you have?'

"Two reasons: I had some wonderful teachers who showed me there's an incredible opportunity to have a personal impact on individuals. That's amazing.

"And secondly, through lots of extra-curricular activities - I was a cadet, a leader in the school's Christian group and a prefect and a peer support leader - all those opportunities showed me I loved helping people grow in a very individual, personal way."

His mother, he said, was horrified - he could do anything, and he wanted to teach?

"It's a sad story," he said of his mother.

"Mum could speak 17 or 18 different languages. She saw that I had a love for language and communication ... so my mum was delighted in that. 'You've got a wonderful career in law ahead of you.'

"She was desperately disappointed when I said this is where I felt like I was being drawn. I say it's sad because she actually passed away in my first year of university after a long fight with cancer. So she never got to see where I am and that I love what I do."

Mr Woo started videoing his classes in late 2012 because a student was sick with cancer and missing a lot of school. Worried about the student falling behind, he started filming and uploading his classes for the boy.

Wootube grew from there, with a steadily - not exponentially (right, Mr Woo?) - growing audience that has spiked during every HSC period.

This month in a major speech to educational leaders, NSW Department of Education secretary Mark Scott singled out Mr Woo as exemplar of the type of person the department wanted to lure into the profession - not just students from the top 30 per cent but from the top 3 per cent.

Mr Scott said the education system would like "to clone Eddie" and was "searching for many more like him."

Universities have been blamed for dropping ATAR entries for teachers in recent years and effectively lowering the academic standards of the cohort entering the profession, while also generating too many teachers for the job market in Australia.

The state government has introduced reforms including minimum literacy and numeracy standards and personality assessments in an attempt to raise standards; and to lure high-performing students to the profession.

Mr Woo doesn't have a silver bullet for the government on that, but he said teaching has incredible rewards. Here's why in his own words:

"I didn't come into this profession because of the pay... I chose it because I saw a really clear purpose," he said.

"Autonomy, mastery and purpose are better motivators than just financial incentives. And teaching has all of those in spades."