A memorial service will be held at The Kings School on Friday to farewell former student Thomas Kelly who was killed in Kings Cross on July 7.
Police said Mr Kelly was out partying with friends at about 10pm when he was king hit from behind.
He was rushed to St Vincent’s Hospital but never regained consciousness and died the following morning.
Friends and family will join students past and present for a funeral service in the school’s War Memorial Chapel.
Headmaster Tim Hawkes said The Kings community was now closing ranks for one of its own.
‘‘There has been close communication between the Kelly family and his alma mater, The Kings School,’’ Dr Hawkes said.
‘‘We have been in constant contact with the family and have offered pastoral support to Thomas' younger brother, who is still at the school.’’
Mr Kelly graduated from The Kings School last year and had just started a cadetship with major accounting firm Hall Chadwick.
He leaves behind a younger sister and brother along with his parents Ralph and Kathy Kelly.
They told the Sydney Morning Herald their son was a ‘‘courageous boy’’ whose life was ‘‘finally taking off’’’.
Mr Kelly appealed for his son’s attacker to come forward.
The attacker is described as being in his 20s, solidly built, Caucasian in appearance and 170 centimetres tall with short brown hair.
Police said the man he punched before striking Thomas suffered a cut above his eye but continued on his way.
Anyone with information can contact Crime Stoppers on 1800 333 000.