Four teenage boys have worn skirts to school in protest at being disciplined for wearing shorts on the hottest day.
The year nine students at Longhill High School in Rottingdean, East Sussex, were among about 20 boys who wore PE shorts instead of trousers on Tuesday.
Some were sent home, and others kept in isolation and excluded the next day.
When the four boys turned up in school skirts on Thursday, head teacher Kate Williams said they could "wear any part of the agreed school uniform".
The mother of 14-year-old Michael Parker, who was one of the group, said three of the boys were initially told to remove the skirts, but all four of them kept them on.
Angela Parker said they wore them to school again on Friday, and were joined by a further 10 boys.
The PE shorts worn by the boys on Tuesday were an official part of the uniform, bearing the school logo.
Pupils who changed out of the shorts and back into trousers were not disciplined.
In a statement on Tuesday, Ms Williams told The Argus: "Students have access to water in order to keep themselves hydrated. We have made reasonable steps to ensure that classrooms are as comfortable as possible.
"I have high standards regarding uniform, and today, in the warm weather conditions, these high standards have been challenged by approximately two percent of parents/students."
Another of the pupils, Kodi Ayling, said he put his trousers back on as he did not want to be excluded from school, but when he wore the skirt, Ms Williams "okayed it and said it was alright".
His father, Wesley Allen, said he hoped the protest would persuade the school to reconsider its school uniform policy.
Longhill High School has now broken up for the summer holidays.