Juelz Trice came home from school earlier this year with permanent marker ink scribbled on his scalp, but it was not a prank played by one of his fellow seventh-graders. It was a punishment enacted by some of the staff.

The boy’s parents filed a federal civil rights lawsuit this week and have told the Guardian they believe the act, a hapless attempt to hide a “fade” haircut with a design that violated the school district’s dress code, was rooted in racism and left him humiliated.

“I was disappointed that they did that to his hair, I was disappointed that I was not notified before it got to the point of them deciding to colour in his hair. I was shocked, I just couldn’t believe it,” said his mother, Angela Washington.

“I definitely think that it would not have happened to a white kid. I can bet my last dollar that it would not have happened.”

The family’s lawyer, Randall Kallinen, said that the decision to use a “jet-black Sharpie”, rather than a colour that aligned more closely with the boy’s brown skin tone, is suggestive of deep-seated racial stereotypes.

“There are hardly any African Americans in America with jet black skin,” the lawsuit states. “It is commonly understood among scholars and the general public that depicting African Americans with jet black skin is a negative racial stereotype. During the Jim Crow era slaves were often depicted as happy in their slave existence and with jet black skin as a means to disguise their humanity and imply that they are unlike ‘white’ people.”

The incident happened in April at Berry Miller junior high school in Pearland, a city of about 150,000 people 15 miles south of downtown Houston. The lawsuit alleges that a school discipline clerk, an assistant principal and a teacher laughed as they took part in the colouring. All three are white, according to the complaint.

Kallinen pointed to federal statistics which show that in Pearland Independent School District black students accounted for 15.9% of enrolments but more than 30% of in-school suspensions, out-of-school suspensions and expulsions in 2015. White students were disciplined at a lower rate.

A government report published in 2018 that examined the national picture found disparities in discipline rates, with black students making up 15.5% of all public school students but representing about 39% of suspended students. Implicit bias is a likely cause.

Washington said that neither she nor Juelz’s father, Dante Trice, were contacted before the colouring. Had they been called, she said, they would have promptly changed his hair so it conformed with the rules. The lawsuit states that Juelz was offered the choice of being isolated from the rest of the class during an in-school suspension or having his hair coloured, and felt obliged to choose the latter rather than have a suspension on his previously unblemished record.

Soon after the incident first made news, Pearland ISD issued a statement which said that filling in hair designs with a marker “is not condoned by the district and does not align with appropriate measures for dress code violations”.

It added: “District administration has contacted the student’s family to express our sincerest apology and extreme disappointment in this situation, which does not fall in line with the values of Pearland ISD.”

Washington said that she was unsatisfied with the response and disappointed that the assistant principal was later promoted, which, she felt, was “kind of like a slap in the face”.

The lawsuit asks for unspecified monetary damages and for racial sensitivity training for school district employees. It claims that the ink “took many days of scrubbing to come off” and the boy “was immensely humiliated and shamed”.

The school district implemented a new, more permissive, hairstyle code for the current academic year, as part of rules which it said seek to “remove any perceived racial, cultural and religious insensitivities”.

In February, New York City issued a new anti-discrimination rule for hairstyles. “Bans or restrictions on natural hair or hairstyles associated with black people are often rooted in white standards of appearance and perpetuate racist stereotypes that black hairstyles are unprofessional,” the guidelines state.

Juelz has just started eighth grade.

“He’s embarrassed, he definitely wants it to go away, he hates talking about it, he doesn’t like the situation at all,” Washington said. “I feel sorry for him because it’s something that he’s going to have to remember for the rest of his life when right now it’s his eighth-grade school year, he should be having fun doing kid things instead of everybody in the school saying, ‘I saw you on the news’.”