The Queen has stressed the importance of education in building a better future and overcoming conflict, Aids, inequality and poverty.
Young people are needed to overcome global challenges, said the Queen
In her 2005 Commonwealth Day Message she said education was the "key to unlocking human potential".
More than half of the Commonwealth's citizens were under 25 giving a "strong foundation" for the future, she said.
In his Commonwealth Day speech, Tony Blair spoke of the importance of education in building communities.
He said the UK would use its presidency of the G8 this year to focus on Africa and climate change while working for security, stability and sustainable prosperity during its EU presidency.
"The Commonwealth provides a unique forum for global diplomacy, one where consensus prevails in decision-making," he said.
The Queen said in her message - broadcast to nations throughout the Commonwealth - we face "significant challenges".
"Some people live in conditions of conflict or insecurity. Others have suffered the impact of natural disasters, such as flooding or hurricanes, which can cause great damage to their communities and countries," she said.
"Quite how destructive this can be became apparent with the devastating Indian Ocean earthquake and tsunami, and the hurricane in the Caribbean last September.
The Commonwealth is an association of countries which used to make up the British empire
"Overcoming these global challenges, whether as individuals or nations, depends on human ingenuity and commitment. It involves young people in particular having the chance to develop their talents and their abilities - without being held back by inequality.
"In my lifetime, I have often seen that when people are encouraged to develop their skills of writing and reasoning, they are well placed to contribute their ideas and energies towards building a better future.
"The key to unlocking human potential, and creating opportunity, is education.
"Education is sometimes described as the golden thread that binds the Commonwealth. Our shared use of a common, world language - English - has underpinned a long and rich tradition of education co-operation.
"With our shared practices and similar systems, an extensive network of scholarships, and many examples of excellence, have been achieved.
"That work continues as the Commonwealth responds to today's new challenges. In our association, where around 75 million children lack access to basic education, one clear objective is the UN Millennium Development Goal of achieving universal primary education by 2015.
"Another is the mitigating effects of HIV and Aids, two-thirds of whose sufferers around the world are Commonwealth citizens, and which in some member countries each year causes the death of more teachers than can be met by newly qualified replacements."