Schools and teachers need to actively tackle the radicalisation of students outside of the classroom, to prevent more young men and women joining groups such as Islamic State (Isis), former prime minister Tony Blair has said.

Speaking at the Global Education and Skills Forum 2015 in Dubai, Blair said that students in developed countries were being exposed to "informal education" networks, and that teachers and education professionals needed to be more vigilant in identifying and tackling extremism.

"We are all talking about education in the classroom but people don't just get educated nowadays in the classroom. They taking influences from all sorts of sources – the internet, from informal education. Wherever intolerance is you have got to go out and tackle it," he said.

"You have millions of young people being taught a very narrow view of the world and often a prejudiced of the world and that can happen even in a country like ours. I hope and assume that is not what they are being taught in the school, but they are getting those influences from outside."

Blair spoke during a panel discussion with Rwandan Prime Minister Paul Kagame, which also covered the successes and failures of the Millenium Development Goals, one of which was to achieve 90% enrollment in primary education.

The media were forbidden from asking questions during the forum, but moderator Fareed Zakaria asked the former prime minister about the three British girls who travelled to Syria to join IS at the end of February.

He was also asked about the role of faith schools in Britain in light of growing divisions between religious communities Europe, to which he replied that though he remained a supporter it was important that young people were taught about the existence of other faiths.

"I think that I can say faith schools only work if they are integrated into the wider system. It is important that young people are taught about other faiths, and are taught in a constructive way… You have to be careful," he said.

"If you do have faith schools you have to be careful… You have to educate young people that someone may be a Muslim or a Hindu or a Jew, but actually here is what he have in common."