Zaid Sher was last seen near his school in Chislehurst at about 9pm on Tuesday May 10.
Shortly before 1.30am on Wednesday May 11, staff realised he was missing and called the police.
Zaid is Asian, about 5ft4ins tall and he is from Newham.
The schoolboy was last seen wearing white Islamic dress, with a black jumper and jogging bottoms underneath.
His disappearance is completely out of character, police said.
Officers, school staff and his family are growing increasingly concerned for his welfare,
Police are appealing for the public’s help to find the youngster, and anyone who sees Zaid should call 999 immediately.
Anyone who has other information about his whereabouts is asked to call police on 101 or tweet @MetCC, quoting 394/11MAY.
Information can also be provided to the Missing People charity on 116 000.