'At this moment in time, police are treating this case as a "missing persons' incident".'
He added: 'This is obviously distressing news for (the boy's) family, friends and the wider Ark Globe community.
'Our hopes and prayers are with the family at this very difficult time.'
The principal acknowledged that the past year has been 'very difficult' for everyone and urged parents to contact the school or NSPCC, the UK's top children's charity, if they need help.
The teenager had been wearing his full uniform as he made his way to The Ark Globe Academy in Southwark, London, on Tuesday at around 8am when he fell from the bridge (emergency services at the scene)