Logan Taylor-Johnstone, from Reigate, Surrey, began Year 4 with a similar hairstyle to the one he had last year, except his hair was lighter and a bit longer.
Teachers at Royal Alexandra and Albert boarding school said his hair was too “extreme” and didn’t fit the school’s policy.
Logan’s parents, Joe Johnstone and Joanne Taylor, both 32, later admitted they used Sun-In, which amplifies the lightening effect of the sun on blonde hair. They did not expect this to fall foul of strict school rules around hair colour.
“I am flabbergasted, I’m stunned,” said Johnstone. “I have asked them several times what is extreme about his hair and they said the length and colour.”
Johnstone continued: “Logan had the same hairstyle before he broke up for the summer and no-one said anything to me then.
“The only difference is that he’s got a longer fringe. I agree it needs a bit of a trim, but it’s not getting in his way.
“And I wouldn’t have said blonde is an extreme colour. He spent a lot of time outside over the summer.”
The school said Logan’s hairstyle is “extreme” because his fringe hangs below his face and his brown roots are beginning to show.
In an email sent on Monday 12 September, the school said: “According to our behavioural policy Logan’s hair is on an extreme fashion and we would recommend that his hairstyle is moderated.”
In a reply to the letter, Johnstone said: “Until a couple of weeks ago I sported the same hairstyle as him and my hair was perfectly acceptable for work in an office. I only cut it because I got too hot.”
The school has since agreed to let Logan’s hair colour grow out. He is unable to shave it off because that would also be considered too “extreme”.
But Johnstone, who has now offered to trim Logan’s hair, is furious with the school’s conduct, and said their approach was “impersonal and unprofessional”.
“If they had said: ‘Just to let you know, Logan’s hair gets in his way when he’s working, could you trim the fringe?’ I would’ve said ‘no problem’,” he said.
“But going on about how it’s an extreme fashion and extreme colour - I would consider having a multi-coloured Mohawk extreme or Nazi symbols shaved into his head.”
Ines Salman, who sent the email on behalf of the headmaster, said: “The policy says ‘children with extreme hair styles’ and his hair isn’t part of the uniform.
“His hair is bleached and is very dark between the roots and the bleached part is very light.
“He does have a very long fringe, it’s difficult for him to work at school.”
Headmaster Mark Dixon said: “The policy about pupil appearance has been determined by the school’s governing body and details are sent to every parent before a child start’s at the school.
“The policy states that ‘hair may not be of an extreme fashion or extremely coloured’.
“It is my view that the request made to Mr Johnstone regarding the colour and length of his son’s hair is entirely consistent with his policy.”