It was a major milestone for the 5-year-old, who was born with spastic diplegia cerebral palsy, and had spinal surgery at the St Louis Children’s Hospital, in the United States, last year.
The surgery helped to release the muscle tension in his legs and meant he was able to walk on his own using a frame.
As Harry left the gates of Abbotsford School yesterday, completing his first day, his mother Bex Finch became emotional.
"We have got this far, I just keep thinking how lucky Harry is to be here and now he’s going to school."
Mrs Finch did not think she would cry when she dropped him and his twin brother, Ollie, off at school in the morning, but said she became suddenly overwhelmed.
"I thought, oh I will be fine I won’t be that emotional, and then as soon as I arrived here at school ... I could not stop crying.
"They are in the big wide world now."
Despite it being a daunting new chapter, she knew Harry would be in safe hands.
"It is such an incredible school ... Harry is going to be really well looked after," she said.
The school had also done up a ramp for him to use, which he was excited about and had talked about all day.
"He just takes everything in his stride," Mrs Finch said.
But the experience was bittersweet.
Harry would face hip surgery on both hips as early as next month.
"The surgery in America was great for [muscle] tightness, but what has happened is his ball in his hip is coming out of the socket by over 50%, that is making one leg longer than the other," she said.
It meant he was not able to use his walker as often, as the risk of dislocating his hips had increased significantly.
It would also mean a slight set back, as he would need to build up his strength again after the next surgery.
"His whole journey has been a roller-coaster," Mrs Finch said.
"Sometimes it feels like it’s one step forward two steps back ... but in the long run it is going to be really positive for him."
