< This article has been updated. See final paragraph
Under the agreement announced yesterday, Lessons for Life, which was founded by the TV company Liberty Global, becomes a subsidiary of Street Child.
No staff have lost their jobs as a result of the merger, a statement from the charities said, with the charities employing a combined 50 people.
A spokeswoman for Street Child said the merger would help the charities reach more children across the globe.
The charities are aiming for a combined income of approximately £20m a year by 2022, the spokeswoman said. Street Child had an income of £14m in the year to 31 March 2018, according to the charity, and Lessons for Life's latest annual accounts show it had an income of £3.3m in 2017.
The chair of Lessons for Life, Andrea Salvato, is now the co-chair of the combined charity with Anthony Wallersteiner, chair of Street Child.
The exact make-up of the new board has yet to be confirmed, the spokeswoman said, but will include trustees from both charities.
Prescott Price, chief executive of Lessons for Life, has become the chief operating officer of the merged charity, with Tom Dannatt remaining as chief executive of Street Child.
The merged charity is based at Street Child’s premises in Stockwell, south London.
The merger takes place 15 months after Street Child merged with Children in Crisis, the charity founded by Sarah, Duchess of York.
Dannatt said: "To bring on board Lessons for Life and a corporate partner of the calibre and scale of Liberty Global, with the commitment they have shown to African children’s education year on year for 10 years is a fantastic step forward for our mission."
Salvato said: "We are hugely excited by, and committed to, the merger with Street Child. The combination of the two charities is going to be incredibly powerful, helping even more children in Africa get a decent education and go on to realise their full potential."
< This article has been updated to show the full income for Street Child, not just Street Child UK