A school student in the US has refused to answer an maths question, labelling it "offensive".

Rhythm Pacheco, 10, was completing her homework when she came across the question: "The table to the right shows the weight of three Grade 4 students. How much heavier is Isabel than the lightest student?"

She circled it, wrote: "This is offensive. Sorry I won't right this it's rood [sic]."

Proud mum Naomi Pacheco with her daughter Rhythm, 10. (Naomi Pacheco)

Rhythm's mother Naomi spotted the response as her daughter finished her homework, proudly sharing it on Facebook.

The schoolgirl has since received praise from around the world, though has admitted that at first she was worried about how her teacher would respond.

"Way to go Rhythm," wrote one Facebook follower. "Love how strong of a person you are at a young age. This will serve you well in life."

She circled the question and labelled it 'offensive'. (Naomi Pacheco)

Another said: "As someone who grew up as an overweight child in the 70's I can tell you it was absolutely brutal. Zero tolerance was not a thing, kudos to this child for being sensitive to others' disabilities."

Rhythm later explained her response to the exam question, writing a letter that was shared by Today in the US. "I don't want to be rude but I don't think that maths problem was very nice because that's judging people's weight," she wrote.

"Also the reason I did not do the sentence is because I just don't think that's nice. Love Rhythm."

The girl later explained her response in a letter shared by US Today. (Naomi Pacheco)

The 10-year-old added she thought the question could be damaging to young girls who already feel insecure about their bodies.

"Rhythm's dad and I were extremely proud of Rhythm for listening to her gut instincts and standing up for what is right," her mum said. "Rhythm's teacher was so responsive and handled the situation with such care.

"She told her she understands how she would be upset about this and that she didn't have to write out the answer."