Gabriel Sousa, aged 13, was walking home with a friend when a man jumped out of a van and attacked him outside Abbeyfield Primary School, Pitsmoor.
The teenagers had just finished lessons at Parkwood Academy, Shirecliffe, and Gabriel was moments away from his Pitsmoor home when violence flared at 3.50pm on Thursday, May 6.
He was punched and knocked to the ground, where he was kicked in his head during the attack in broad daylight.
Gabriel, who lives with his Portuguese mum and five siblings, suffered a fractured eye socket in the attack and may need surgery.
He also suffered concussion and has not been able to return to school since the attack because of his injuries.
His mum Carla, a 38-year-old cleaner, said the incident was witnesses by passers-by and has been reported to South Yorkshire Police.
She is keen for officers investigating the incident to retrieve CCTV footage from nearby cameras in a bid to track down the attacker, who jumped out of a van while the driver remained in the vehicle.
Carla also wants other witnesses to come forward to help police trace the culprit.
She said: “A woman got in touch who witnessed this and said my son did nothing wrong, he was just walking home.
“He was pushed to the ground and when he was laid there he was kicked in his head and was then left there unconscious.
“What kind of man could do that to a child and then walk away knowing he was unconscious? He could have killed him.
“If he can do this to my child, what can he do to others?”
She said her son has been left scared to be alone since the attack.
“He wants to stay close to me since this happened and can’t understand why it happened to him,” she said.
“It has scared him.”
Anyone with information should call South Yorkshire Police on 101 or Crimestoppers on 0800 555111.
Quote incident 14/7092/21.
South Yorkshire Police has been approached for a statement.