She said: “He was insistent this summer.
“I was very surprised when he did it as it was a gutsy thing to do.
“You do just have to take a stand, otherwise nothing’s going to change.”
She added that the introduction of a summer uniform is the “only way forward”.
“It’s definitely something with climate change – summer’s are a lot hotter than when we were at school now. It’s just not fair on the children,” she said.
“Oscar often says he can’t concentrate and he gets very hot and sweaty, feeling ill sometimes when he gets hot at school.”
Head teacher at Ysgol Bro Dinefwr, Eirian Davies, said: “With the weather now warming we will be monitoring the situation in classes and across the school to ensure temperatures are comfortable for everyone.
“We have [on Friday] allowed pupils the option of wearing their PE kit and will notify parents of any further changes in good time.”