Shelley Saunders said that her grandaughter Renae and foster child Katie were both taken out of their classes at Birley Academy last week after dyeing their hair.
Katie, 13, turned up to school with short purple hair while Renae, 12, arrived with long hair dyed burgundy.
The school, which has a strict natural hair policy, placed both girls in isolation on Wednesday and Thursday before Shelley decided to pull them out of class on Friday.
This morning, the Hackenthorpe resident said that Renae ‘broke down in tears’ after once again being told that she would be placed in isolation if she did not adhere to the policy.
Shelley said that the two girls have been left devastated by the school’s decision and raised concerns about the impact it will have on their education.
“Katie has had a number of mental health problems and expresses herself by changing her hair colour a lot,” Shelley explained.
“The school put them in isolation`n on on Wednesday and Thursday and told them they had to correct their hair colour before being allowed back into class.
“On Friday, the school again tried to put them in isolation so I told them to come home because they're not learning anything in there.
“I went up to the school this morning with the kids but was told the same thing again. My grandaughter burst out the school crying so I’ve had to bring them home again.”
Following the row, Shelley said that she does not want to dye the girls’ hair back to its normal colour out of principle and added that she cannot understand how the rule is affecting their learning.
“The girls are not handling the situation well at all. Katie is telling me that she doesn't want to stay there because of everything that’s happened.” Shelley explained.
“I’m really worried about the impact this is having on their mental health and their education. They’re not getting taught anything whilst they're in isolation.
“I think it’s a ridiculous rule. I don’t think their hair colour is stopping them from learning. I don’t know what to do now but I don’t want to dye their hair back out of principle.
“It’s such a sad situation. Katie is so clever and used to love school but now I can’t get her up and out of bed in the mornings because she doesn't want to be there.”
A Birley Academy spokesperson said: “Our school policy clearly outlines our expectations and all school procedures have been followed regarding this matter.”