The new schools and children secretary has spoken of his "honour and responsibility" at his promotion.
Ed Balls will head up the newly created Department for Children and Families, which has been crafted from the now defunct Department for Education and Skills.
As secretary of state for children, schools and families, Mr Balls will be responsible for children and young people's education.
With the Conservatives increasingly taking the initiative on all-round child wellbeing, Mr Balls will also lead cross-departmental policies.
He will target child poverty, children's health issues including obesity and youth sport, and promote the "respect" agenda.
Mr Balls said: "Every parent wants their child to get the best possible start in life and have the best chance to do well in school.
"Our responsibility will be to support families and ensure that all children and young people are safe and healthy, that they secure the highest standards of achievements, that they enjoy their childhood."
He promised to drive up standards in every school and prevent youth offending.
The prime minister said education would be his passion in government and immediately moved to reform the department.
Responsibility for higher education has been transferred to the newly created Department of Innovation, Universities and Skills, which also absorbs science and innovation.
New secretary John Denham said his department would help everyone realise their skills and opportunities.
The NUT, however, questioned the wisdom of splitting the department.
Steve Sinnott, general secretary of the NUT, said "history teaches us that the need to apply a joined up approach across the various phases always leads back to unity."
Nevertheless, he welcomed Mr Balls appointment as secretary and credited the MP with a "wealth of ideas and energy."
Mr Brown also stamped his mark on government by disbanding the Department for Trade and Industry. It has been replaced with the Department for Business, Enterprise and Regulatory Reform, which will work with Department of Innovation, Universities and Skills.