Jaron Smith managed to scale the boundary before strolling ten minutes across busy main roads to his house in West Yorkshire.
His mother Jade said she couldn’t believe her eyes when her son walked through the door and has called the incident “appalling.”
She said Jaron climbed the fence at Cobblers Lane Primary School in Pontefract, on Thursday and walked thorough the front door - just under half a mile away - at 1pm.
Miss Jarratt, 23, said: “I couldn’t believe it, I was at home and Jaron just walked in through the front door.
“At first I thought he had got into trouble and been brought home by a teacher, but he was on his own.
“The incident is appalling. It’s not a bad school by any means but you put a lot of trust in teachers to look after your children and this has made me doubt that.
“Anything could have happened to Jaron. He had to cross Baghill Lane on his way home, which is a busy road. He could have been hit by a car or someone could have taken him.”
Headteacher Karen Briggs said she was confident school staff followed procedures when dealing with the incident and the family had been kept “fully informed.”
Mrs Briggs said: “The safety and well being of all pupils is always a top priority in our school.
“However, we are never complacent when it comes to child safety and will be reviewing this to see if there’s anything we could have done to prevent this happening.
“We kept the family fully informed during the incident. The parents brought the child back to school on the same day.
“When we spoke to the parents they said they were happy with how the school had dealt with the incident.
“Teachers have spoken to pupils and have reiterated the importance of not climbing the fence or leaving school premises unsupervised.”
But Miss Jarratt said: “The first thing I heard from the school was when I was on my way to take Jaron back there.
“The headteacher rang to ask if Jaron had turned up at home.
“It’s a good job he had as nobody from the school had gone after him.
“I am far from happy about the way the school dealt with the incident.”