A boy of 15 was knocked unconscious in an unprovoked attack in Rottingdean.
The Longhill School pupil was walking home along a footpath when a man in a balaclava running towards him hit him in the face.
The force of the blow knocked the lad off his feet. He fell down an embankment and hit his head on a tree, leaving him out cold.
The boy, who lives locally, was found two hours after the attack by a member of the public.
The incident took place at around 4pm yesterday on a footpath in the wooded area at the west end of Court Ord Road leading to the Rottingdean allotments.
The attacker was described as aged in his early twenties, 6ft 2in tall with a medium build and wearing a black balaclava and camouflage trousers.
Detective Constable Tracey Dixon, of Brighton CID, said: “The unprovoked assault left the victim in a potentially serious and vulnerable condition.
“PCSOs have been supporting the investigation team in conducting house-to-house inquiries and we are now following a number of lines of inquiry.
“Police have spoken to local residents and the man has been seen in the area in the last six months.
“If anyone has seen this man or has any information about this assault they should contact us immediately.
“There is nothing to suggest the boy was targeted for being a student.”
Longhill head teacher Haydn Stride has sent a message to parents, staff and pupils saying: “I am writing to inform you of a serious incident that took place last night after school.
“A student was the victim of a robbery whilst walking home alone in the wooded area from school.
“The person is described by the police as a male of average height wearing camouflage trousers and a black balaclava.
“Our students have been informed and have been told to dial 999 if this person is seen and not to approach.
“Police and CID will be carrying out increased patrols around the school at this time.”
Anyone with information is asked to contact Sussex Police on 0845 6070999 or to call the independent charity Crimestoppers anonymously on 0800 555111.
