Byron Enguix was walking on a school crossing outside St John's Catholic Primary School when he was hit by a vehicle on Wednesday afternoon.

The seven-year-old was just a few steps ahead of his father Heath and brother Ethan, 10, when the incident occurred about 3.25pm.

Byron's mum Rosemary Enguix said a male red P-plate driver was behind the wheel. He stopped once before allegedly driving off.

"My husband saw a P-Plater screeching towards him and braking for about 15 metres. He hit Byron while on the crossing," she said.

"Byron was thrown about a metre-and-a-half in the air and landed on his bottom, fortunately not his head.

"Byron was struck in the stomach and abdominal area.

"My son was hysterical. Heath picked him up and the police were called, they arrived within minutes.

"The P-plater just drove off. I can't believe someone could do that."

Byron was rushed to Campbelltown Hospital on Wednesday afternoon.

He was transferred to the trauma unit at Randwick's Sydney Children's Hospital in the early hours of Thursday morning.

Ms Enguix said Byron underwent a series of tests before being cleared to go home later that day.

"Byron's injuries were very minimal, he had no broken bones," she said.

"But it was quite emotional for Byron."

The Enguix family is appealing for public assistance to identify the alleged driver.

Ms Enguix said the car was a light blue Ford station wagon and was a post-2000 model.

"We want to make sure he is punished for his actions," she said.

"Please call the police if you have any information - we don't want this to happen again."

A St John's Catholic Primary School spokeswoman said there was a regular crossing supervisor for Lindesay Street, however, they were away on Wednesday.

Any witnesses are encouraged to call Campbelltown Police Station on 4620 1199.