Joshua Cunnah, 13, got badly burnt during a trip to a waterpark along with three other pupils from Buile Hill Visual Arts College, in Salford.
One of the four children's parents criticised the teachers, but Wendy Cunnah has backed the school, believing the staff did all they could.
Cunnah, a nursery nurse, told Manchester Evening News: "The children were told numerous times to put suncream on by the teachers.
"My son had Factor 30 which I had packed for him. He put it on before he got to the waterpark and again once he got there.
"But he was having such a good time on the slides, he then forgot to put it on again. He accepts full responsibility."
Upon returning to England, the four pupils all required treatment at the burns unit of the Royal Manchester Children’s Hospital.
Four teachers accompanied the 41 pupils on holiday and headteacher James Inman said the staff did everything they could to warn the children of dangers of being in the sun.
Cunnah said her son called her from Spain to tell her of his burns and she still believes the teachers "could not have done more".
Cunnah's son is currently off school to recover from the burns.
After returning from the trip, another pupil Connor Pritchard, 15, had large blisters on his arm.
His mother, Estelle Pritchard, 37, told The Mirror: "When he stepped off the coach I could see the bulge of the blisters on his arm. He tried to lift his shirt up and I broke down when I saw the burns.
"No teacher hung around to speak to me. I just took one look and said 'right lets get you to hospital'."
Mrs Pritchard called it "total neglect" on the part of the teachers.
The headteacher at Buile Hill Visual Arts College said the school may have to review school trips if children refuse to follow instructions.
School governor and Labour councillor, John Warmisham, told Manchester Evening News: "We have learned a lesson with this trip, but I do think the school did everything it could.
"Parents has to sign contracts before they went which mentioned children had to apply Factor 50 when told to do so."