A high school student has been banned from classes in Tasmania after a dispute over the color of his hair.

Cruise Walsh, 16, claims he is being discriminated against at Hobart's New Town High School after he dyed his hair black with red streaks.

He says the school told him on Friday that until he changed his hair to suit policy guidelines, he would be banned from class.

But the well-spoken 10th grader said he could not understand why he was isolated.

"I felt surprised and shocked, made an outcast by a teacher," he said, after he left school upset only 15 minutes into the school day.

"It's just two red streaks, there are people in the school with five different colors in their hair, and patterns." Cruise said his hair was dyed to help an apprentice hairdresser from a Hobart salon who needed a volunteer for a training assessment last Tuesday.

The hairdresser passed her test.

"Many people have said it looks good. Some teachers said they liked it," he said.

Cruise said his workplace, Salamanca Bakehouse, did not have a problem with it.

New Town principal Darryl Moir said Cruise walked out on assistant principal Ian Cordwell. Moir said Cruise's behavior was "unacceptable" when Cordwell tried to talk with him. He said the school had a student code of conduct.

He said the code clearly detailed the student uniform and stated that extreme hairstyles and colors were not acceptable.

"Natural-colored dyed hair is fine. Cruise dyes his hair black and that is fine, but bright colors are against our policy," he said.

Cruise's mother Jennifer Walsh described the school's actions as "disgusting and outrageous."

The Education Department said each school had the power to develop its own student code of conduct and enforce it.

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