Colin Hegarty, from Preston Manor School in Wembley, has reached the final stages of a competition to find the world’s most exceptional teachers.
The winner will receive a prize of a $1m (£690,000) at an awards ceremony in March.
Mr Hegarty said it was good to see a competition that “elevated the status of teachers”.
The Global Teacher Prize, set up by the Varkey Foundation, the charitable arm of the Gems international education firm, is aimed at “unearthing thousands of stories of heroes that have transformed young people’s lives”.
The final top 10 shortlist has been published, after entries were received from teachers in 148 countries.
Mr Hegarty is the only UK finalist, alongside teachers from the United States, Australia, India, Finland and Kenya.
The shortlist also includes Aqeela Asifi, who teaches refugees in Pakistan, and Hanan Al Hroub who grew up in a Palestinian refugee camp and is now a teacher.
Mr Hegarty describes maths as “quite addictive” and has set up a website with videos teaching how to solve maths problems.
The idea began when one of his pupils had to go overseas to care for his sick father – and Mr Hegarty put materials online so that he could keep up with his maths lessons.
Mr Hegarty, who rejects the idea that some people are inherently “good at maths”, says that the subject lends itself to being taught through online videos, because pupils can benefit from looking at something repeatedly until they understand.
He says there is no simple “formula” for what makes a good teacher, but he says that like being a good student, it can be about sticking at it.
Mr Hegarty says this was the lesson he learned from his own family. He grew up in a London council flat and went on to get a first-class degree in maths from Oxford University.
He has already won a UK prize, in the national teaching awards run by Pearson.
Last year’s global teacher prize winner was Nancie Atwell from the United States, who donated her prize money to her school. Richard Spencer from Middlesbrough had reached the top 10.
Sunny Varkey, founder of the Varkey Foundation, said he wanted the prize to “shine a powerful spotlight on the incredible work teachers do all over the UK and throughout the world every day”.
Since last year’s prize, Mr Varkey announced that he was signing up for the Giving Pledge, in which the very wealthy promise to give away most of their money to philanthropic causes.