Thirteen was an unlucky number for young mathematicians from Croydon primary schools competing against teams across London in a maths final.
The 13 teams in the Count on Us London contest played games of 24, where each team must use the given numbers and operations to make the number 24.
And the three finalist primary schools from Croydon - Harris Primary Benson, Harris Primary Kenley and Rowdown Primary – narrowly missed out on winning.
Instead they were all given certificates and a medal for taking part from maths legend Johnny Ball.
Mr Ball, who is the Mayor’s Fund for London’s numeracy ambassador, said: “The 24 game is a great example of how we can engage with children to make maths fun.
“Numeracy is one of the most important things we can teach young people today."