We all know the importance of education. Everyone aspires to have a good one, but its quality and availability is not the same for all. This situation changes as social, economic and political conditions change and technological development provides new benefits and threats.

The Organisation for Economic Co-operation and Development (OECD), which promotes policies that will improve the economic and social well-being of people around the world, has been looking at the future of global education. Its head of education, Andreas Schleicher, has been talking to the BBC about some major international trends affecting education systems around the world.

One threat is the widening gap between rich and poor, with more intense pockets of extreme privilege and deprivation. In OECD countries, the richest 10% have incomes 10 times greater than the poorest 10%. This inequality is a challenge for schools who want to offer equal and fair access to education for everyone.

Another trend is the rising affluence in Asia. It's suggested that a large rise in the middle-classes in China and India will increase demand for university places. Andreas Schleicher asks the question "What values will these newly wealthy consumers want from their schools?"

Increasing migration will also have an impact on education systems. Mobility results in more culturally diverse students eager to learn and develop a good life for themselves. But that can be a challenge, too, as Andreas Schleicher asks: "How should schools support pupils arriving from around the world? What questions does it raise about identity and integration? Will schools have a bigger role in teaching about shared values?"

Funding pressure is another issue: as our demand and expectation for education rises and more people go to university, who's going to pay for it all? The rise in dependency on technology is another concern. What should students learn when many of their talents can be replicated by machines? And how reliant should we be on learning from the internet?

These are just some of the issues the OECD is highlighting. But they remain irrelevant for hundreds of millions of the world's poorest children who don't even have access to school places or receive such low-quality education that they leave without the most basic literacy or numeracy.