The experience was nothing like he had expected. "The students were from families of a lower economic and social status," he recalls. "They had no interest in studying. They liked to spend their time running around or fighting with each other."
Realising the futility of teaching these 14- to 16-year-olds from a textbook, he came up with a new idea. "I asked them to think up a business idea that'd interest them. I told them I'd help them set it up and they could keep the money if it was profitable."
The students latched onto the idea and came up with a variety of business plans from selling smoothies in schools to designing artfully painted trainers.
Ravenscroft also took them to visit companies. "I wanted them to see what a real working environment was like," he says. "I hoped it would give them some incentive to work hard for their future."
His efforts paid off. He saw a marked change in his students' attitude to learning.
"Their skills improved and they were more engaged in class," the teacher says.
Buoyed by his idea's success, he set up Enabling Enterprise, a non-profit organisation, in London in 2009. It offers training programmes to schools and helps turn students' ideas into community projects. To date, 9,000 students from 80 British schools have benefited from it.
One project has involved helping a school to set up a shop to sell products made by and offer services provided by students. It has got as many as 600 youngsters involved. Ravenscroft's work has earned him the UK Entrepreneurship Teacher of the Year and Teacher First Excellence awards.
"The best way to motivate students to learn is to make them learn by taking action. This way, they can see how their skills are relevant to the real world," he says.
"Social innovation is about finding a new way to solve a problem. Every individual has the power to do that."
Last month, Ravenscroft ran a two-day workshop in Hong Kong on social innovation as part of MaD (Make a Difference), a creative platform for young people run by the Hong Kong Institute of Contemporary Culture. "Social innovation is a relatively new concept in Hong Kong," says Ada Wong Ying-kay, the institute's honorary executive director. "I hope this can motivate young people to find creative solutions to bring about social change."
Maggie Chong Jwo-ruey, 22, agrees: "Tom has inspired me to make a change." The University of Hong Kong student is now working on a project to educate people about over-consumption.