A 17-year-old local boy was attacked by another teenager as he walked along Hempstead Road, Uckfield on Saturday ( March 19).
The victim, who was walking with friends, was approached by a group of four boys around 7.00pm.
An altercation is believed to have taken place and the teenager was punched on the jaw and fell to the ground sustaining a head injury.
He was taken to Hurstwood Park Neurological Hospital for treatment to a fractured skull and remains in a stable but serious condition.
A 17-year-old boy from Eastbourne was arrested on suspicion of GBH in the early hours of Sunday (March 20 ) and has been bailed until April 20 pending further enquiries.
DC Helen Upton from Wealden CID said: “The attack happened in a residential area and I am appealing for witnesses or anyone who has information about the attack to please contact us.”
If anyone has any information that could help police with their enquiries they are asked to contact Sussex Police on 0845 60 70 99 quoting serial 1369 of 19/3 or anonymously to the independent charity Crimestoppers on 0800 555 111.