Leah Thomas, 16, died her long naturally dark hair red before heading to classes at Ivybridge Community College.
But the GCSE pupil was put in isolation and then sent home by teachers at the South Devon school until she changes her new do.
The school has said she can come back to classes when her hair “meets the published requirements”.
But her father Owen has accused the staff of “making an example” of his daughter.
He said: “She dyed her hair two weeks ago and my wife and I didn’t think of it as being an issue.
“It’s not loud, or garish. It’s just a dark shade of red. She came back from school last week and said she had been asked to tie it up.
“That wasn’t a problem. But this morning, I got a call from her head of year saying Leah had been put in isolation and taken out of her classes.
“He told me that school policy didn’t allow red hair and that she was setting a bad example to the Year Seven pupils.
“It’s absolutely ridiculous. She’s a good kid and has never been involved in anything like this before.
“She only has a few weeks left until she does her exams and the school seem quite happy to let her miss lessons and put her education at risk.”
Owen and wife Beth were called to the school to collect their daughter on Wednesday after she was removed from lessons.
She is yet to return to classes, but Owen said his daughter will now remove the dye in order to return to school before her exams.
But he said pupils should be allowed to express themselves and not be made to conform.”
He added: “If a pupil is happy at school, they’re going to learn better.
“The school have made an example of Leah simply for being herself. I don’t think anyone should be made uncomfortable for how they look.”
School deputy principal Gill Taylor said: “Many schools adopt different approaches to school uniform.
“Given the breadth of the current educational landscape, this is a benefit to parents in enabling them to choose a school that they believe meets their values and offers the style of education they deem most appropriate for their children.
“The student has been asked to attend College when their uniform, including hairstyle, meets the published requirements. This can easily be resolved.”